FSH
Romantic love is associated with changes in the sex hormones testosterone, follicle-stimulating hormone, and luteinizing hormone ( Marazziti and Canale, 2004 ; Durdiakova et al., 2017 ; Sorokowski et al., 2019 ), although the findings have been inconsistent. Testosterone appears to be lower in men experiencing romantic love than controls ( Marazziti and Canale, 2004 ) and higher eros scores are associated with lower levels of testosterone in men ( Durdiakova et al., 2017 ). Lower levels of testosterone in fathers are associated with greater involvement in parenting (see Storey et al., 2020 , for review). The direction of testosterone change in women is unclear (see Marazziti and Canale, 2004 ; Sorokowski et al., 2019 ). Sex hormones are involved in the establishment and maintenance of sexual characteristics, sexual behavior, and reproductive function ( Mooradian et al., 1987 ; Chappel and Howles, 1991 ; Holloway and Wylie, 2015 ). Some sex hormones can influence behavior through their organizing effects resulting from prenatal and postnatal exposure. In the case of romantic love, however, the effects of sex hormones on the features of romantic love are the result of activating effects associated with behaviorally contemporaneous activity. It is possible that sex hormones influence individual differences in the presentation of romantic love through their organizing effect (see Motta-Mena and Puts, 2017 ; Luoto et al., 2019 ; Arnold, 2020 ; McCarthy, 2020 , for descriptions of organizing and activating effects of testosterone, estradiol, and progesterone). Changes in sex hormones could help to explain the increase in sexual desire and arousal associated with romantic love ( Hatfield and Sprecher, 1986 ; Hatfield and Rapson, 2009 ; Diamond and Dickenson, 2012 ).
Romantic love is associated with decreased serotonin transporter density ( Marazziti et al., 1999 ) and changes in plasma serotonin ( Langeslag et al., 2012 ), although inconsistencies have been found in the direction of change according to sex. In one study, men experiencing romantic love displayed lower serotonin levels than controls and women displayed higher serotonin levels than controls ( Langeslag et al., 2012 ). Decreased serotonin transporter density is indicative of elevated extracellular serotonin levels ( Mercado and Kilic, 2010 ; Jørgensen et al., 2014 ). However, decreased levels of serotonin are thought to play a role in depression, mania, and anxiety disorders ( Mohammad-Zadeh et al., 2008 ), including obsessive-compulsive disorder (for a discussion of the relationship between serotonin and OCD, see Baumgarten and Grozdanovic, 1998 ; Rantala et al., 2019 ). One study showed that a sample of mainly women (85% women) experiencing romantic love have similar levels of serotonin transporter density to a sample of both women and men (50% women) with obsessive-compulsive disorder ( Marazziti et al., 1999 ), which could account for the intrusive thinking or preoccupation with the loved one associated with romantic love ( Hatfield and Sprecher, 1986 ).
Lower dopamine transporter density and lower dopamine transporter maximal velocity in lymphocytes have been found in people experiencing romantic love ( Marazziti et al., 2017 ). This is indicative of increased dopamine levels ( Marazziti et al., 2017 ) and is consistent with neuroimaging studies (e.g., Takahashi et al., 2015 ; Acevedo et al., 2020 ) showing activation of dopamine-rich regions of the mesolimbic pathway. One study ( Dundon and Rellini, 2012 ) found no difference in dopamine levels in urine in women experiencing romantic love compared with a control group. Dopamine is involved in reward behavior, sleep, mood, attention, learning, pain processing, movement, emotion, and cognition ( Ayano, 2016 ). Up-regulation of the dopamine system could help to explain the motivational characteristics of romantic love such as longing for reciprocity, desire for complete union, service to the other, and maintaining physical closeness ( Hatfield and Sprecher, 1986 ).
There are no studies that have specifically investigated oxytocin levels in romantic love (at least none that measure romantic love with a validated scale). However, studies ( Schneiderman et al., 2012 , Schneiderman et al., 2014 ; Ulmer-Yaniv et al., 2016 ) have demonstrated that people in the early stages of their romantic relationship have higher levels of plasma oxytocin than controls (singles and new parents). We infer this to mean that reciprocated romantic love is associated with elevated oxytocin levels. Oxytocin plays a role in social affiliation ( IsHak et al., 2011 ) and pair-bonding ( Young et al., 2011 ; Acevedo et al., 2020 ). Oxytocin receptors are prevalent throughout the brain including in the mesolimbic pathway (e.g., Bartels and Zeki, 2000 ). Elevated oxytocin could account for many of the behavioral features of romantic love such as actions toward determining the other’s feelings, studying the other person, service to the other, and maintaining physical closeness ( Hatfield and Sprecher, 1986 ).
Romantic love has been associated with elevated cortisol levels ( Marazziti and Canale, 2004 ), although this has not been replicated ( Sorokowski et al., 2019 ), and one study measuring cortisol in saliva found the opposite ( Weisman et al., 2015 ). Different results could be attributed to different length of time in a relationship between the samples (see Garcia, 1997 ; de Boer et al., 2012 ). Cortisol plays a role in the human stress response by directing glucose and other resources to various areas of the body involved in responding to environmental stressors while simultaneously deactivating other processes (such as digestion and immune regulation, Mercado and Hibel, 2017 ). Elevated cortisol levels may play a role in pair-bond initiation ( Mercado and Hibel, 2017 ) and are indicative of a stressful environment.
Romantic love is associated with higher levels of nerve growth factor, and the intensity of romantic love correlates with levels of nerve growth factor ( Emanuele et al., 2006 ). Nerve growth factor is a neurotrophic implicated in psycho-neuroendocrine plasticity and neurogenesis ( Berry et al., 2012 ; Aloe et al., 2015 ; Shohayeb et al., 2018 ) and could contribute to some of the neural and endocrine changes associated with romantic love.
Despite “madness” being mentioned in one review of the neurobiology of love ( Zeki, 2007 ) and psychopathology being discussed in studies investigating the endocrinology of romantic love (e.g., Marazziti et al., 1999 , 2017 ), the similarities between romantic love and psychopathology are under-investigated. An understanding of the mechanisms that regulate addiction, mood disorders, and anxiety disorders may help to shed light on the psychological characteristics and mechanisms underlying romantic love and identify areas for future research.
Conceptualizing romantic love as a “natural addiction” (e.g., Fisher et al., 2016 ) not only helps to explain romantic love’s psychological characteristics but provides insight into the mechanisms underlying it (e.g., Zou et al., 2016 ). For example, a neurocircuitry analysis of addiction, drawing on human and animal studies, reveals mechanisms of different “stages” of addiction that have implications for romantic love: binge/intoxication (encompassing drug reward and incentive salience), withdrawal/negative affect, and preoccupation/anticipation ( Koob and Volkow, 2016 ). Each of these stages is associated with particular neurobiological activity and each stage could be represented in romantic love. This may mean that the findings of studies investigating the neurobiology of romantic love (which rely primarily on studies where visual stimuli of a loved one are presented) equates to the binge/intoxication stage of addiction. Findings from studies investigating romantic rejection ( Fisher et al., 2010 ; Stoessel et al., 2011 ; Song et al., 2015 ) may equate to the withdrawal/negative affect stage of addiction. Findings from resting-state fMRI studies ( Song et al., 2015 ; Wang et al., 2020 ) may equate to the preoccupation/anticipation stage of addiction. The result is that current neuroimaging studies may paint a more detailed picture of the neurobiology of romantic love than might initially be assumed.
Mood is an emotional predictor of the short-term prospects of pleasure and pain ( Morris, 2003 ). The adaptive function of mood is, essentially, to integrate information about the environment and state of the individual to fine-tune decisions about behavioral effort ( Nettle and Bateson, 2012 ). Elevated mood can serve to promote goal-oriented behavior and depressed mood can serve to extinguish such behavior ( Wrosch and Miller, 2009 ; Bindl et al., 2012 ; Nesse, 2019 ). Anxious mood is a response to repeated threats ( Nettle and Bateson, 2012 ). Because romantic love can be a tumultuous time characterized by emotional highs, lows, fear, and trepidation, and can involve sustained and repetitive efforts to pursue and retain a mate, it follows that mood circuitry would be closely intertwined with romantic love. Additionally, because romantic love concerns itself with reproduction, which is the highest goal in the realm of evolutionary fitness, it makes sense that mood may impact upon the way romantic love manifests. Understanding the mechanisms that regulate mood can provide insights into psychological characteristics of romantic love and the mechanisms that regulate it. No studies have directly investigated the mechanisms that contribute to changes in mood in people experiencing romantic love. However, insights can be taken from research into the mechanisms of mood and anxiety disorders.
While addiction, hypomania, depression, and anxiety symptoms in people experiencing romantic love may be the normal manifestation of particular mechanisms, symptoms associated with psychopathology may be the manifestations of malfunctioning mechanisms as a result of evolutionary mismatch (see Durisko et al., 2016 ; Li et al., 2018 ). As a result, the mechanisms that cause romantic love and those that cause psychopathology may not be precise models with which to investigate the other. Nonetheless, the mechanisms that cause psychopathology may provide a useful framework with which to base future research into romantic love. Conversely, it may also be that our understanding of the mechanisms that cause romantic love could be a useful framework with which to further investigate psychopathology.
The drug reward and incentive salience features of the binge/intoxication stage of addiction involve changes in dopamine and opioid peptides in the basal ganglia (i.e., striatum, globus pallidus, subthalamic nucleus, and substantia nigra pars reticulata, Koob and Volkow, 2016 ). No research has investigated opioids in romantic love, despite them being involved in monogamy in primates (see French et al., 2018 ) and pair-bonding in rodents ( Loth and Donaldson, 2021 ). The negative emotional states and dysphoric and stress-like responses in the withdrawal/negative affect stage are caused by decreases in the function of dopamine in the mesolimbic pathway and recruitment of brain stress neurotransmitters (i.e., corticotropin-releasing factor, dynorphin), in the extended amygdala ( Koob and Volkow, 2016 ). No studies have investigated corticotropin-releasing factor in romantic love. The craving and deficits in executive function in the preoccupation/anticipation stage of addiction involve the dysregulation of projections from the prefrontal cortex and insula (e.g., glutamate), to the basal ganglia and extended amygdala ( Koob and Volkow, 2016 ). No studies have investigated glutamate in romantic love. There are at least 18 neurochemically defined mini circuits associated with addiction ( Koob and Volkow, 2016 ) that could be the target of research into romantic love. It is likely that romantic love has similar, although not identical, mechanisms to addiction (see Zou et al., 2016 ; Wang et al., 2020 ).
Similar to the brain regions implicated in romantic love, the ventral tegmental area has been associated with mania ( Abler et al., 2008 ), the ventral striatum has been associated with bipolar disorder ( Dutra et al., 2015 ), and the amygdala has been associated with the development of bipolar disorder ( Garrett and Chang, 2008 ). These findings should be interpreted with caution, however, as replicating neuroimaging findings in bipolar disorder has proven difficult (see Maletic and Raison, 2014 ). Research implicates two interrelated prefrontal–limbic networks in elevated mood, which overlap with activity found in romantic love: the automatic/internal emotional regulatory network which includes the ventromedial prefrontal cortex, subgenual anterior cingulate cortex, nucleus accumbens, globus pallidus, and the thalamus, and the volitional/external regulatory network which includes the ventrolateral prefrontal cortex, mid- and dorsal-cingulate cortex, ventromedial striatum, globus pallidus, and thalamus ( Maletic and Raison, 2014 ).
Norepinephrine (theorized to be involved in romantic love, e.g., Fisher, 1998 , 2000 ), serotonin, dopamine, and acetylcholine play a role in bipolar disorder ( Manji et al., 2003 ). One study ( Dundon and Rellini, 2012 ) found no difference in norepinephrine levels in urine in women experiencing romantic love compared with a control group. No studies have investigated acetylcholine in romantic love but romantic love is associated with serotonin ( Marazziti et al., 1999 ; Langeslag et al., 2012 ) and dopamine activity ( Marazziti et al., 2017 ). Similar to the endocrine factors implicated in romantic love ( Emanuele et al., 2006 ; Schneiderman et al., 2012 , 2014 ; Ulmer-Yaniv et al., 2016 ), bipolar patients in a period of mania have also demonstrated higher oxytocin ( Turan et al., 2013 ) and nerve growth factor ( Liu et al., 2014 ) levels and lower levels of serotonin ( Shiah and Yatham, 2000 ). Additionally, there is some evidence that women diagnosed with bipolar disorder present with higher levels of testosterone whereas men present with lower levels of testosterone compared with sex-matched controls ( Wooderson et al., 2015 ). Similar findings have been found in romantic love ( Marazziti and Canale, 2004 ). Dysfunction in the hypothalamic–pituitary–adrenal axis, where cortisol plays a major role, has also been implicated in bipolar disorder ( Maletic and Raison, 2014 ). Cortisol probably plays a role in romantic love ( Marazziti and Canale, 2004 ; Weisman et al., 2015 ).
Neuroimaging studies have implicated changes in functional connectivity in the neural circuits involved in affect regulation in people experiencing depression ( Dean and Keshavan, 2017 ). Increased functional connectivity has been found in networks involving some of the same regions, such as the amygdala, the medial prefrontal cortex, and nucleus accumbens in both people experiencing romantic love and people who recently ended their relationship while in love ( Song et al., 2015 ).
There are a number of endocrine similarities between romantic love and depression. One major pathophysiological theory of depression is that it is caused by an alteration in levels of one or more monoamines, including serotonin, norepinephrine, and dopamine ( Dean and Keshavan, 2017 ). Altered dopamine transmission in depression may be characterized by a down-regulated dopamine system (see Belujon and Grace, 2017 ), which is inferred from numerous human and animal studies, including successful treatment in humans with a dopamine agonist. In romantic love, however, dopamine appears to be up-regulated, especially in areas of the mesolimbic pathway (e.g., Marazziti et al., 2017 ; Bartels and Zeki, 2000 ; Acevedo et al., 2020 ). This could account for some findings that romantic love is associated with a reduction in depression symptoms ( Bajoghli et al., 2013 , 2017 ). However, these need to be reconciled with contrasting findings that romantic love is associated with increased depression symptoms ( Bajoghli et al., 2014 ; Kuula et al., 2020 ) and evidence suggesting that a relationship breakup in people experiencing romantic love is associated with depression symptoms ( Stoessel et al., 2011 ; Price et al., 2016 ; Verhallen et al., 2019 ). The mechanisms that underlie depression might provide a framework for such efforts.
Dysregulation of the HPA axis and associated elevated levels of cortisol is theorized to be one contributor to depression ( Dean and Keshavan, 2017 ). Changes in oxytocin and vasopressin systems (theorized to be involved in romantic love, e.g., Fisher, 1998 , 2000 ; Carter, 2017 ; Walum and Young, 2018 ) are associated with depression (see Purba et al., 1996 ; Van Londen et al., 1998 ; Neumann and Landgraf, 2012 ; McQuaid et al., 2014 ). No studies have investigated vasopressin in people experiencing romantic love. There is also decreased neurogenesis and neuroplasticity in people experiencing depression ( Dean and Keshavan, 2017 ), the opposite of which can be inferred to occur in romantic love because of its substantial neurobiological activity and elevated nerve growth factor (see Berry et al., 2012 ; Aloe et al., 2015 ; Shohayeb et al., 2018 ).
The insular cortex, cingulate cortex, and amygdala are implicated in anxiety and anxiety disorders ( Martin et al., 2009 ). There is also evidence that cortisol, serotonin and norepinephrine are involved ( Martin et al., 2009 ). The substantial overlap between the mechanisms regulating romantic love and those causing anxiety and anxiety disorders provides an opportunity to investigate specific mechanistic effects on the psychological characteristics of romantic love. Assessing state anxiety and these mechanisms concurrently in people experiencing romantic love may be a fruitful area of research.
There is also a need to clarify the role of the serotonin system in romantic love. Similar serotonin transporter density in platelets in people experiencing romantic love and OCD suggests a similar serotonin-related mechanism in both ( Marazziti et al., 1999 ). However, lower serotonin transporter density in platelets is indicative of higher extracellular serotonin levels ( Mercado and Kilic, 2010 ; Jørgensen et al., 2014 ). This is despite lower levels of serotonin being theorized to contribute to anxiety ( Mohammad-Zadeh et al., 2008 ). One study found lower circulating serotonin levels in men experiencing romantic love than controls and higher levels of circulating levels of serotonin in women experiencing romantic love than controls ( Langeslag et al., 2012 ). Insights from the mechanisms regulating anxiety disorders may help to provide a framework with which to further investigate the role of the serotonin system in romantic love and reconcile these findings.
Positive illusions are cognitive biases about a relationship and loved one that are thought to have positive relationship effects ( Song et al., 2019 ). The research into positive illusions does not use samples of people explicitly experiencing romantic love, and instead uses people in varied stages of a romantic relationship, including those in longer-term pair-bonds. One study ( Swami et al., 2009 ), however, did find a correlation between the “love-is-blind bias” (one type of positive illusion) and eros scores. We also know that cognitive biases resembling positive illusions do exist in romantic love. Both the Passionate Love Scale (e.g., “For me, ____ is the perfect romantic partner,” Hatfield and Sprecher, 1986 , p. 391) and the eros subscale of the Love Attitudes Scale (e.g., “My lover fits my ideal standards of physical beauty/handsomeness,” Hendrick and Hendrick, 1986 , p. 395) include questions about a respondent’s loved one that resemble measures of positive illusions. Understanding the mechanism that regulates positive illusions will provide a model against which the mechanisms regulating the cognitive features of romantic love can be assessed.
A proposed mechanism of positive illusions includes the caudate nucleus, dorsal anterior cingulate cortex, ventral anterior cingulate cortex, orbitofrontal cortex, ventrolateral prefrontal cortical regions, and dorsal medial prefrontal cortex ( Song et al., 2019 ). These regions overlap with the brain regions associated with romantic love. This suggests that the cognitive biases associated with romantic love may be related to, but are distinct from, positive illusions. Targeted neuroimaging studies could ascertain any involvement of the ventrolateral prefrontal cortex and the dorsal medial prefrontal cortex in romantic love. Such research could help to delineate a mechanism that specifically regulates one cognitive aspect of romantic love from those that regulate other psychological aspects of romantic love.
It is not possible to say with any certainty if other animals experience romantic love. Some certainly engage in pair-bonding and exhibit behaviors that are characteristic of romantic love such as obsessive following, affiliative gestures, and mate guarding (see Fisher et al., 2006 ). While some similarities between humans and other animals may be the result of parallel evolution, an understanding of the mechanisms involved in pair-bond formation in other animals can raise questions and guide research into romantic love in humans. Research into monogamous prairie voles, in particular, has identified neurobiological and endocrinological mechanisms that regulate pair-bonding processes. Drawing on this research, a hypothetical neural circuit model of pair-bond formation (pair-bonding) that includes the ventral tegmental area, nucleus accumbens, paraventricular nucleus, amygdala, hippocampus, anterior olfactory nucleus, and medial prefrontal cortex has been proposed ( Walum and Young, 2018 ). Research implicates oxytocin, vasopressin, dopamine, and, potentially, serotonin and cortisol in pair-bonding ( Walum and Young, 2018 ). Most of these neural regions and endocrine factors have been implicated in romantic love in humans. The implications of this research become apparent when the phylogeny of romantic love is presented.
When applied to romantic love, the second of Tinbergen’s (1963) four questions asks: “How does romantic love develop over the lifetime of an individual?” This can be answered with reference to the age of onset of romantic love, its presence throughout the lifespan, and its duration. Questions of ontogeny also encompass issues around the internal and external influences on romantic love ( Tinbergen, 1963 ; Zeifman, 2001 ). We have also chosen to include some consideration of culture in this section because it influences the causes of romantic love. We find that romantic love first develops in childhood, is experienced at all ages in both sexes, usually lasts months or years, but can exist for many years or decades. It is influenced by a range of internal and external factors and is similar across cultures. The modern environment may influence romantic love in ways not present in our evolutionary history.
Romantic love occurs from childhood through adulthood. It first manifests before puberty ( Hatfield et al., 1988 ), with boys and girls as young as four reporting experiences that equate to romantic love. Adolescence is the time in which romantic love first manifests with all of its characteristic features ( Hatfield and Sprecher, 1986 ), including the onset of sexual desire and activity and, potentially, pair-bonding. Romantic love may be more common among adolescents than young adults. In one study ( Hill et al., 1997 ), American university psychology students reported a greater occurrence of mutual and unrequited love experiences when they were 16–20 years old compared to when they were 21–25 years old. However, romantic love exists at all ages of adulthood in both sexes ( Wang and Nguyen, 1995 ).
There are few studies of psychological sex differences in romantic love. Those that exist (e.g., Hatfield and Sprecher, 1986 ; Hendrick and Hendrick, 1995 ; Cannas Aghedu et al., 2018 ) compare the overall intensity of romantic love and find no difference or slightly more intense romantic love in women than men. To our knowledge, no research has specifically investigated sex differences in duration or form of romantic love although it has been shown that some precursors to romantic love may play a greater role in one sex than the other (see Pines, 2001 ; Sprecher et al., 1994 ; Riela et al., 2010 ). As highlighted above, there are small sex differences in the neurobiology of romantic love ( Bartels and Zeki, 2004 ; Fisher et al., 2006 ) and sex differences may exist in the activity of testosterone ( Marazziti and Canale, 2004 ) and serotonin ( Langeslag et al., 2012 ) in people experiencing romantic love, although findings have been inconsistent. These neurobiological and endocrinological differences may, presumably, have differential effects on the presentation of romantic love which have not yet been identified by research.
The psychological features of romantic love are said to normally last between 18 months to 3 years ( Tennov, 1979 ), although studies have found that serotonin transporter density, cortisol levels, testosterone levels, follicle-stimulating hormone levels, and nerve growth factor levels do not differ from controls 12–24 months after initial measurement ( Marazziti et al., 1999 ; Marazziti and Canale, 2004 ; Emanuele et al., 2006 ). Unrequited love has been shown to last an average duration of between 10 and 17 months, depending on the type of unrequited love ( Bringle et al., 2013 ). In that study, unrequited love for someone that an individual pursued lasted the shortest period of time (10.12 months) and romantic love for someone who an individual knows but has not revealed their love to lasted the longest (18.44 months) in a sample of high school and university students from the United States. This contrasts with reciprocated romantic love that lasted even longer (an average of 21.33 months).
The early stages of romantic love characterized by stress may be distinct from a later period characterized by feelings of safety and calm ( Garcia, 1997 ; de Boer et al., 2012 ). The first stage, which is characterized by approximately the first 6 months of a relationship, has been described as “being in love.” It is marked by all the characteristics of romantic love, including, especially, romantic passion and intimacy. The second phase, which has been said to last from approximately 6 months to 4 years, has been referred to as “passional love.” During this time passion is maintained but commitment and intimacy increase. Passional love gives way to companionate love, passion subsides, and commitment and intimacy reach their peaks. While a description of these phases is informative, it is important to recognize that only one study has investigated these phases and they used a sample of predominately university students ( Garcia, 1997 ). Mechanisms research has not adopted these stages and “early stage” romantic love does not specifically refer to the first 6 months of a romantic relationship.
Romantic love exists on a continuum of intensity but can be classified categorically ( Hatfield and Sprecher, 1986 ). The authors of the Passionate Love Scale ( Hatfield and Sprecher, 2011 ) have developed arbitrary cutoffs for differing intensities of romantic love. However the thresholds that define them are not theoretically or empirically derived and are yet to be widely accepted in the literature.
Romantic love can commence abruptly or build up slowly, although the phenomenon of “love at first sight” may actually be strong attraction rather than romantic love, per se ( Sternberg, 1986 ; Zsok et al., 2017 ). In one study of Chinese and American participants, 38% of participants fell in love fast and 35% fell in love slow, with the remaining unknown ( Riela et al., 2010 ). Another study, of Iranians, found that 70% of participants fell in love slowly or very slowly ( Riela et al., 2017 ). Romantic love can end abruptly but often wanes slowly.
Regardless of the normal duration of romantic love, there is a general inverse relationship between the length of time in a relationship and romantic love ( Hatfield et al., 2008 ; Acevedo and Aron, 2009 ). Romantic love normally gives way to failure of a relationship to form, a relationship breakup, or transition to companionate love. However, in some individuals, romantic love can last many years, or even, decades ( O’Leary et al., 2011 ; Acevedo et al., 2012 ; Sheets, 2013 ). In romantic relationships that last, romantic love serves to bond partners together by creating shared understandings, emotions, and habits ( Hatfield and Walster, 1985 ) characteristic of companionate love and long-term pair-bonds. The transition from romantic love to companionate love is gradual and both types of love share many characteristics. In circumstances where romantic love is maintained beyond the initial few years, obsessive thinking about a partner is no longer a feature (e.g., Acevedo and Aron, 2009 ; O’Leary et al., 2011 ).
A number of internal and external influences affect when, with whom, and how we fall in love. The scenario of attachment, separation, and loss in young children ( Bowlby, 1969 , 1973 , 1980 ) is similar to a “desire for union” and may be the groundwork for romantic attachments in later life ( Hatfield et al., 1988 ). To this extent, romantic love, like newborn/infant attachment, is “prewired” into humans as part of their evolutionary heritage ( Hatfield et al., 1989 ). Researchers “focus their investigations on the effects of mother-infant bonding in order to explain variations in the form, duration, and/or frequency of adult passionate relationships” ( Fisher, 1998 , p. 31). For example, a person’s adult attachment style is determined in part by childhood relationships with parents ( Hazan and Shaver, 1987 ) and this may have implications for the experience of romantic love (e.g., Hendrick and Hendrick, 1989 ; Aron et al., 1998 ). Romantic love is positively associated with a secure attachment style and negatively associated with an avoidant attachment style.
Precursors to romantic love include reciprocal liking, appearance, personality, similarity, social influence, filling needs, arousal, readiness, specific cues, isolation, mysteriousness, and propinquity (see Aron et al., 1989 ; Sprecher et al., 1994 ; Riela et al., 2010 ; Riela et al., 2017 ; see also Hazan and Diamond, 2000 ; Fisher, 2011 ). Research also suggests that conscious variables (personality and appearance), situational variables (proximity and arousal), lover variables (lover finds us attractive, lover fills important needs, similarity, and lover is best friend), and unconscious variables (similarity to relationship with parents, similarity of lover to father, similarity of lover to mother, and love at first sight) contribute to with whom we fall in love ( Pines, 2005 ). The majority of precursors are an interplay between internal and external influences.
Some of the most important precursors to romantic love include personality, reciprocal liking, physical appearance, propinquity, specific cues, readiness, and similarity ( Aron et al., 1989 ; Sprecher et al., 1994 ; Riela et al., 2010 , 2017 ). Personality is the “attractiveness of the other’s personality (e.g., intelligent, humorous)” ( Riela et al., 2010 , p. 474). This represents an interplay between internal influences (the preferences of the individual or what they find attractive) and external influences (the personality characteristics of the potential loved one). Reciprocal liking has been defined above and is a mixture of internal and external influences. Physical appearance, too, is an interplay between what an individual finds attractive, either through genetic predisposition or learned experience, and the physical attributes of the potential loved one. Propinquity has been defined and discussed above and is a combination of internal and external influences. Similarity is “having things in common, including attitudes, experiences, interests, and personal factors such as appearance, personality, and family background ( Riela et al., 2010 , p. 474). This is contingent upon both the individual’s characteristics (internal influence) and the potential loved one’s characteristics (external influence).
There are, however, some precursors that are explicitly internal or external influences. Readiness is “being emotionally or physically prepared for seeking a romantic relationship, such as having just broken up with someone and seeking comfort in a new partner” ( Riela et al., 2010 , p. 475). This can be a largely internal influence that can cause romantic love. Specific cues are “particular characteristics of the other (e.g., smile, shape of the eyes), that are relevant to the perceiver in producing strong attractions. This is not the same as attractiveness in general but refers to highly idiosyncratic features of potential love objects that are specifically important to the individual” ( Riela et al., 2010 , p. 475). These are largely external influences that cause romantic love, although they do trigger a biological or psychological response which is internally determined.
There have been a number of books (e.g., Jankowiak, 1995 , 2008 ) and studies that shed light on the cross-cultural nature of romantic love. The sum of research indicates that romantic love is probably universal (although the research is yet to prove this unequivocally) with relatively few psychological differences found between cultures (although cultures respond to love in different ways). An ethnographic analysis of 166 cultures from the Standard Cross-Cultural Sample ( Jankowiak and Fischer, 1992 ; Jankowiak and Paladino, 2008 ) found no evidence of romantic love in only 15 cultures, and this was largely due to lack of data. Validated measures of romantic love (i.e., Passionate Love Scale, Love Attitudes Scale, Triangular Love Scale) have been used in at least 50 countries ( Feybesse and Hatfield, 2019 ). The Triangular Theory of Love is robust cross-culturally ( Sorokowski et al., 2020 ). Cross-cultural accounts of the features and the intensity of romantic love are remarkably similar (see Feybesse and Hatfield, 2019 for a review of cross-cultural perspectives on romantic love). Multiple neuroimaging studies have ascertained that the same neural mechanisms associated with romantic love in American samples are associated with romantic love in Chinese samples ( Xu et al., 2011 , 2012b ).
Romantic love may be thought of more positively among Western countries than other countries and Westerners report falling in love more often (see Feybesse and Hatfield, 2019 ). Cultural differences have also been identified in the role of precursors in causing romantic love. A comparison between Japanese, Russian, and American populations found that culture played a role in the self-reported importance of personality, physical appearance, propinquity, similarity, readiness, isolation, mystery, and social standing ( Sprecher et al., 1994 ). Some differences have also been found between Chinese and Americans ( Riela et al., 2010 ) and between Iranians and Americans ( Riela et al., 2017 ) using similar and different methods. In some cultures, romantic love is suppressed and arranged marriages predominate (discussed below).
The evolutionary mismatch hypothesis argues that humans are now living in environments vastly different from those in which they evolved and, as a result, biological mechanisms may not interact with the environment in the manner that they originally evolved to Li et al. (2018) . Adaptations may malfunction. This has implications for the functioning of mechanisms and psychology. Evolutionary mismatch may influence the occurrence, duration, form, and experience of romantic love. As already suggested, evolutionary mismatch may influence the degree to which certain social mechanisms play a role in causing romantic love. This may have flow-on impacts on the frequency with which an individual falls in love or with whom they fall in love. The increased exposure to potential mates may also lead to greater instances of relationship dissolution and new instances of romantic love than would have been the case in our evolutionary history. Evolutionary mismatch may also influence the duration of romantic love. Under evolutionary conditions, romantic love would usually occur in the context of reproduction, pregnancy, and childbirth (see Goetz et al., 2019 ). This may mean that the duration of romantic love may have been shorter in females than is the case in modern developed societies because they are overcome by mother-infant bonding, possibly at the expense of romantic love.
The form and experience of romantic love may also be impacted by evolutionary mismatch. Technology means that lovers are able to maintain regular contact (e.g., by telephone) or be exposed to images of the loved one (e.g., by photographs) in the absence of physical contact. This consistent exposure may be associated with more frequent activation of neural structures associated with romantic love (i.e., reward and motivation structures) and change the intensity or subjective experience of romantic love compared to evolutionary ancestors who may have been completely separated for periods of time.
When applied to romantic love, the third of Tinbergen’s (1963) four questions asks: “What are the fitness-relevant functions of romantic love?” Functional explanations address the fitness ramifications (survival and reproduction) of the behavior or trait of interest ( Tinbergen, 1963 ; Zeifman, 2001 ; Bateson and Laland, 2013 ). We are, thus, concerned with both the fitness-relevant benefits and costs of romantic love. We have outlined the benefits and costs of romantic love associated with five functions based on a small literature on the subject (i.e., Fletcher et al., 2015 ; Buss, 2019 ), reproduction-related literature, and our consideration of the subject. Some of the benefits we describe can be considered functions in their own right (e.g., Buss, 2019 ). Table 3 presents a summary of benefits and costs of romantic love according to five distinct yet interrelated functions: mate choice, courtship, sex, pair-bonding, and health. Our approach is to describe each function, present the benefits associated with each function, and present the costs associated with each function. Where relevant, we have included information about related concepts or theories. We contend that while there is a small amount of evidence for the health promoting benefits of romantic love, the evidence is insufficient to say with certainty that health promotion is a function of romantic love. We conclude this section by summarizing some potential selective pressures and describing romantic love as a complex suite of adaptations and by-products.
Reproduction- and survival-related benefits and costs associated with each function of romantic love.
Reproduction-related: | ||
Mate choice | Conserve mating energy, choose between potential mates, focus attention on preferred mates (♀/♂) | Imperfect mate choice, excluding other potential mates, detract from other goals, unwanted love experience (♀/♂) |
Courtship | Pursue potential mates, secure a mate prepared to commit, display commitment, signal fidelity, learn about and assess potential mates, display reproductively relevant resources (♀/♂); Signal paternal investment (♂) | Expenditure of time and resources, embarrassment, obsessive pursuit, stress, intrasexual competition, costly courting (♀/♂) |
Sex | Reputation and status gain, sex is pleasurable, sex promotes bonding (♀/♂); Providing sexual access, increased fecundity (possibly) (♀); Gaining sexual access (♂) | Unwanted pregnancy, parenting responsibilities, damage to reputation and status (♀/♂), Pregnancy followed by a period of lactation, risk of single parenthood (♀) |
Pair-bonding | Establish pair-bonds, provision of psychological and emotional resources, caregiving, promote fidelity, promote jealousy, promote relationship exclusivity through mate guarding, promote mate retention tactics, sharing resources, reputation and status gain, increased offspring survival (possibly), promote fitness interdependence, promote self-expansion (♀/♂); Paternal investment (♀); Promote actions that lead to successful reproductive outcomes, co-parenting (♂) | Missed long-term mating opportunities, restricted short-term mating opportunities, damage to reputation and status, sharing of time and resources, reduced support network, jealousy, harmful relationships, homicide, stalking, grief following breakup, other breakup costs, (♀/♂); Sexual obligation to partner (♀); Parental investment (♂) |
Survival-related: | ||
Health | Active/elated mood, reduced depression symptoms, decreased risk of STI, improved sleep quality (♀/♂); Stronger immune system (♂) | STI, negative mood, major depression, suicide (♀/♂); Sleep alterations, birth-related complications/death, infertility from STI (♀) |
Romantic love serves a mate choice function ( Fisher et al., 2006 ). Both men and women engage in mate choice ( Stewart-Williams and Thomas, 2013 ). Assessing potential mates has important fitness consequences for individuals, as the benefits of finding a suitable mate are often higher than mating haphazardly or with a randomly selected mate ( Geary et al., 2004 ; Andersson and Simmons, 2006 ; Jones and Ratterman, 2009 ; Shizuka and Hudson, 2020 ). On the other hand, mate choice is a costly and error-prone activity and, thus, it may be adaptive to focus one’s attention on a particular mate that has been identified as a preferred partner ( Bowers et al., 2012 ). Romantic love serves this function.
Mate choice evolved in mammals to enable individuals to conserve their mating energy, choose between potential mates, and focus their attention on particular potential mating partners ( Fisher, 2000 ; Fisher et al., 2006 ). The focus of one’s attention on a single potential mate is not without costs (e.g., Klug, 2018 ; Bear and Rand, 2019 ). Imperfect mate choice (e.g., Johnstone and Earn, 1999 ) could result from imperfect information (e.g., Luttbeg, 2002 ) or acceptance or rejection errors. Imperfect information might include the concealment of information that has detrimental effects on fitness. Time to assess an individual is important in mate choice and imperfect mate choice could potentially be a greater problem in circumstances where romantic love is quick to arise. Mate choice, by definition, excludes other potential mates and romantic love, in fact, suppresses the search for other mates ( Fletcher et al., 2015 ). This cost can be exacerbated in certain environments such as those within which finding additional mates is relatively easy ( Kushnick, 2016 ). Romantic love can detract from other fitness-promoting goals such as career-advancing activities, physical health promoting activities, or forming and maintaining other social relationships.
Romantic love serves a courtship function ( Fisher et al., 2006 , 2016 ). Courtship involves a series of signals and behaviors that serve as a means of assessing potential partner quality and willingness to invest in a relationship ( Trivers, 1972 ; Wachtmeister and Enquist, 2000 ). One function of the attraction system is to pursue potential mates ( Fisher, 2000 ). People in love often engage in courtship of their loved one with the aim of persuading them that they are a good long-term mate.
The primary benefit of courtship in romantic love is that it can secure a mate that is prepared to commit to a relationship. To do this, both sexes can pursue potential mates, display commitment, and signal fidelity ( Buss, 2019 ). These acts are why love has been described as a commitment device ( Frank, 1988 ; Fletcher et al., 2015 ; Buss, 2019 ). Courtship allows individuals to learn about and assess the suitability of potential mates while displaying reproductively relevant resources ( Buss, 2019 ). Men emphasize characteristics such as resources, while women emphasize characteristics such as beauty, in an attempt to increase attractiveness ( Buss, 1988 ; Luoto, 2019a ). Men, at least historically, also provide signals of parental investment ( Buss, 2019 ). Literature on human courtship from an evolutionary perspective supports the notion of greater choosiness among females, predicted by parental investment theory ( Trivers, 1972 ), for short-term mating and less serious commitments. This effect, however, substantially diminishes for long-term mating endeavors and marriage commitment ( Kenrick et al., 1990 ). The literature also suggests that women are looking for specific cues, indicative of evolved preferences, during the courtship process ( Oesch and Miklousic, 2012 ).
There are costs associated with romantic love’s courtship function. These include the expenditure of a significant amount of time and resources and, if courtship efforts are not reciprocated, embarrassment ( Silver et al., 1987 ). Sometimes, individuals in love might engage in intrusive “obsessive pursuit” of someone who is not interested ( Spitzberg and Cupach, 2003 ). Courtship can be a particularly stressful time for an individual. There are also potential costs because individuals who are courting might find themselves in direct intrasexual competition with another individual who has an interest in their potential mate. Intrasexual competition can be costly because an individual must divert additional resources to this endeavor. An individual bears even greater costs if they lose this competition. Both sexes can be subject to costly signaling as part of courtship ( Griskevicius et al., 2007 ), although men are at risk of higher fitness costs associated with temporally extended courtships, despite this being interpreted as a sign of a good mate by women ( Seymour and Sozou, 2009 ).
Romantic love promotes sex and may increase the chances of pregnancy. Sex is an important part of romantic relationships and initiation into sex with a partner, and a greater frequency of sex, is associated with the earlier stages of a romantic relationship ( Call et al., 1995 ). Sex and pregnancy are not, however, features of romantic love in pre-pubescent children and pregnancy is not a feature of romantic love in post-menopausal women. The nature of reproduction is different in societies where contraception and family planning practices are widespread (see Goetz et al., 2019 , for review of evolutionary mismatch in human mating). In such circumstances, immediate pregnancy may not be a feature of romantic love, whereas sex often is. In such circumstances, romantic love may indirectly promote pregnancy by creating pair-bonds whose members later reproduce.
Romantic love provides sexual access ( Buss, 2019 ). Love is one of the most common reasons people give for having sex ( Ozer et al., 2003 ; Meston and Buss, 2007 ; Dawson et al., 2008 ; Meston and Buss, 2009 ). Given the relative willingness of men to engage in short-term mating compared to women, it follows that sex because of love plays a greater role in providing sexual access by women to men than the other way around ( Meston and Buss, 2007 ). Sex can facilitate a gain in reputation ( Meston and Buss, 2007 ) and both sexes increase their status by having children ( Buss et al., 2020 ). Sex is intrinsically pleasurable and reinforcing, and promotes bonding ( Meltzer et al., 2017 ). In times before the advent of contraception, repeated sex with a partner would usually result in pregnancy and childbirth ( Goetz et al., 2019 ; Kushnick, 2019 ). This is still the case in many parts of the world.
For example, there is evidence that features characteristic of romantic love may be associated with a greater number of children among the Hadza, a hunter gatherer tribe in northern Tanzania ( Sorokowski et al., 2017 ). Higher passion, which is definitive of romantic love (e.g., Sternberg, 1986 ), is associated with a greater number of children in women. The findings are important because the lifestyle of the Hadza more closely resembles the environment in which humans evolved than do industrialized or agrarian societies. As a result, inferences can be made about the adaptive function of passion in human evolutionary history. However, intimacy, another component of romantic love ( Sternberg, 1997 ), was found to be negatively correlated with number of children in women. Instead, commitment, a feature of companionate love, was associated with greater number of children in both women and men ( Sorokowski et al., 2017 ). Romantic love is normally relatively short-lived, and therefore the methods used in this study may not have been ideally suited to investigate the fitness consequences of romantic love. Nonetheless, this finding provides some support for the notion that romantic love promotes sexual access by women and facilitates reproduction.
One study ( Sorokowski et al., 2019 ) suggests that romantic love may increase the likelihood of a woman falling pregnant. Higher levels of the gonadotropins, follicle-stimulating hormone, and luteinizing hormone, and a non-significant but positive increase in estradiol to testosterone ratio in women experiencing romantic love could cause increased ovarian activity and increased estradiol synthesis, which might result in higher fecundity ( Sorokowski et al., 2019 ).
The costs associated with romantic love’s sex function are far greater for women than for men ( Trivers, 1972 ). Both sexes could be subject to unwanted pregnancy and associated parenting responsibilities (although this impacts women to a greater extent). There is also, however, a risk of damage to an individual’s reputation. Women are often subject to criticism from other women for engaging in sexual activity ( Koehn and Jonason, 2018 ), especially if a long-term relationship does not result. Men and women risk damage to their reputation for having sex with a low mate value partner, although men are generally treated far more favorably than women for engaging in sexual activity (see Zaikman and Marks, 2017 ). For women, a period of pregnancy followed by a lengthy period of lactation may ensue, and this is costly in terms of the ability to obtain sufficient resources and protecting oneself from harm. There is also the possibility that the relationship will dissolve following pregnancy and the woman may be left to raise a child without the father’s support ( Koehn and Jonason, 2018 ).
Romantic love serves a pair-bonding function ( Fletcher et al., 2015 ). Pair bonding is both a process and a sate characterized by the formation of “enduring, selective attachments between sexual partners” ( Young et al., 2011 , p. 1). It differs from established pair-bonds and the neural characteristics of people experiencing romantic love differ somewhat from what is associated with longer-term pair-bonds (see Acevedo et al., 2012 , for distinction). Evolutionarily, when sex more often led to pregnancy, this pair-bonding would occur in the context of pregnancy and childbirth (although it is unclear if romantic love can exist at the same time as mother-infant bonding). This is still the case in many parts of the world. This is one possible reason for the duration of reciprocated romantic love to be between 18 months and 3 years ( Tennov, 1979 ) when not interrupted by childbirth. The intensity of specific neural activity in people experiencing romantic love is associated with relationship maintenance ( Xu et al., 2012a ).
Romantic love can establish long-term pair-bonds. In both sexes, romantic love promotes the provision of psychological and emotional resources ( Buss, 2019 ) as well as other types of caregiving ( Fletcher et al., 2015 ). It promotes relationship exclusivity through fidelity, jealousy, and mate-guarding ( Buss, 2019 ). Both sexes engage in additional mate retention tactics such as vigilance, mate concealment, monopolization of time, resource display, love and care, or sexual inducements ( Buss et al., 2008 ). Romantic love also promotes the sharing of other resources such as food or money. This benefit for women would have been, and often continues to be, greatest during times of lactation (see Marlowe, 2003 ; Quinlan, 2008 ). Both sexes can also benefit reputationally, as being in a relationship with a high mate value individual confers status, and individuals who are married or in a relationship are viewed more favorably than single people ( DePaulo and Morris, 2006 ). Men experiencing romantic love engage in actions that lead to successful reproductive outcomes ( Buss, 2019 ), such as protecting partners from physical harm. Men also engage in parenting ( Geary et al., 2004 ; Bribiescas et al., 2012 ), which could potentially result in increased offspring survival ( Fletcher et al., 2015 ).
When people are experiencing romantic love they are usually, but not always, interested in pursuing a “long-term mating strategy.” A long-term mating strategy is one that involves commitment, pair-bonding, and the parental investment (if children result) of both partners ( Buss, 2006 ). This contrasts with short-term mating strategies that do not often require public commitment, pair-bonding, and parental investment of the father ( Buss and Schmitt, 1993 ). Pair-bonding is characteristic of a long-term mating strategy.
The concept of romantic love serving as a commitment device is relevant to pair-bonding, as are the concepts of fitness interdependence ( Buss, 2019 ) and self-expansion. Fitness interdependence is the degree to which two people influence each other’s success in replicating their genes ( Aktipis et al., 2018 ). Romantic love binds two individuals together so that the potential reproductive success of one person is contingent upon the success of the other. The self-expansion model suggests that “people seek to expand their potential efficacy to increase their ability to accomplish goals” and that “one way people seek to expand the self is through close relationships, because in a close relationship the other’s resources, perspectives, and identities are experienced, to some extent, as one’s own” ( Aron and Tomlinson, 2019 , p. 2). Fitness interdependence and self-expansion can be increased in people experiencing romantic love.
There are substantial costs associated with pair-bonding ( Kushnick, 2016 ; Klug, 2018 ). Both sexes are potentially missing out on long-term mating opportunities with other suitable mates and are more restricted in terms of short-term mating opportunities ( Geary et al., 2004 ). There is a potential for damage to an individual’s reputation if they are in a relationship with a low mate value individual ( Buss, 2016 ). Both sexes share resources. Pair-bonding is associated with a reduction in the size of an individual’s support network ( Burton-Chellew and Dunbar, 2015 ). Jealousy can have negative effects upon a relationship ( Buss, 2000 , 2019 ; Hatfield et al., 2016 ) and there is a potential for emotional or physical harm arising from a relationship. People sometimes engage in homicide of their current or former partners in response to infidelity, or as a result of jealousy or a breakup ( Buss, 2000 , 2019 ; Shackelford et al., 2003 ). Some women engage in this behavior, but it is predominately a male behavior, when it occurs ( Buss, 2019 ). Stalking can occur following a breakup ( Spitzberg and Cupach, 2003 ; Buss, 2019 ) or, more generally, as a result of romantic love ( Marazziti et al., 2015 ). There is the potential for grief or depression symptoms following the breakup of a relationship ( Verhallen et al., 2019 ). Changing living arrangements, dividing up resources, and legal costs could all be necessary following the dissolution of a pair-bond ( Bear and Rand, 2019 ). Sex-specific costs include sexual obligations to a partner from women and parental investment by men ( Geary et al., 2004 ; Luoto, 2019a ).
While there is evidence that successful pair-bonding is associated with better health and survival ( Fletcher et al., 2015 ), there is little evidence showing that romantic love is associated with good health. Falling in love is associated with alteration in immune cell gene regulation in young women ( Murray et al., 2019 ). Specifically, falling in love is associated with genetic changes that could potentially result in an up-regulation of immune responses to viruses.
Experiencing romantic love for a recently gained partner is associated with the “active/elated” symptoms of hypomania ( Brand et al., 2007 , 2015 ). These symptoms are considered as favorable, “bright side” symptoms and contrast with unfavorable “dark side” symptoms such as disinhibition/stimulation-seeking and irritable/erratic dimensions ( Brand et al., 2015 ). Despite their association with hypomania, the favorable nature of these symptoms in romantic love may be a sign of good physical and mental health because higher hypomanic scores have been associated with higher “mental toughness,” increased physical activity, lower symptoms of depression, and lower sleep complaints ( Jahangard et al., 2017 ). Additionally, falling in love with a partner is sometimes associated with a reduction in depressive symptoms ( Bajoghli et al., 2013 , 2017 ). A reduction in the number of sexual partners could result in a decreased risk of sexually transmitted infections. There is evidence that romantic love might sometimes be associated with improved sleep quality ( Brand et al., 2007 ; Bajoghli et al., 2014 ).
There are some health-related costs associated with romantic love for both sexes. Despite a reduced risk of sexually transmitted infections being a benefit of romantic love, engaging in sexual activity at all may represent an increased risk of sexually transmitted infection, resulting in a cost to some ( Buss, 2016 ; Koehn and Jonason, 2018 ). Infertility from sexually transmitted infections is possible among women ( Koehn and Jonason, 2018 ). Disinhibited/stimulation-seeking and irritable/erratic, depressed, and anxious mood are sometimes features of romantic love ( Wang and Nguyen, 1995 ; Bajoghli et al., 2013 , 2014 , 2017 ; Brand et al., 2015 ; Kuula et al., 2020 ). In the face of repeated unrewarding efforts or adverse events in the courtship process, depressed or anxious mood could result ( Nettle and Bateson, 2012 ). Romantic rejection can result in a major depressive episode or even suicide (see Rantala et al., 2018 ). Despite evidence of improved sleep quality in people experiencing romantic love in some studies ( Brand et al., 2007 ; Bajoghli et al., 2014 ), one study ( Kuula et al., 2020 ) found poorer sleep quality, later sleep timing, and shorter sleep duration (one feature commonly found in studies relied upon to suggest a sleep quality benefit of romantic love) in adolescent girls experiencing romantic love. This suggests that altered sleep may in fact be a detrimental cost in some people experiencing romantic love. Women have the added risk of birth-related complications and death, which has been common in humans until recently in developed countries ( Goldenberg and McClure, 2011 ).
The literature contains three interesting theories of possible selective pressures for romantic love. They are framed in the context of promoting the evolution of pair-bonds, but as will be detailed below, the evolution of pair bonds and romantic love are likely to be inexorably linked. All three theories relate to the provision of resources by males to females. The first theory is that pair-bonds and romantic love may have emerged prior to 4 million years ago when bipedalism emerged and hominins moved into the woodlands and savannahs of our ancestral homelands (see Fisher et al., 2016 ). The need for mothers to carry infants in their arms may have driven them to select partners that were wired for pair-bonds which was associated with provisioning, defense, and other forms of support.
The second theory is that biparental care was a driving force in the emergence of long-term mating strategies ( Conroy-Beam et al., 2015 ). A game theoretical approach contends that females selecting males that were wired for pair-bonds directly increased the chances of offspring survival through the provisioning of tangible and intangible resources to the female and offspring. If biparental care was a driving force in the formation of pair-bonds in humans, it would be a uniquely human pressure, as biparental care has been generally identified as a consequence, rather than a cause, of pair-bonds in mammals ( Opie et al., 2013 ; Lukas and Clutton-Brock, 2013 ). This theory also has to contend with the fact that father presence is often not associated with better offspring survival in societies with little access to health care or contraception (see Fletcher et al., 2015 ).
The third theory is that a need for increased fecundity drove the selection of pair-bonds ( Conroy-Beam et al., 2015 ). Periods of malnutrition cause decreased fecundity. Once again, a game theoretical approach suggests that the selection of males that were wired for pair-bonds, which is associated with provisioning of females, increased the caloric intake of females over prolonged periods of time and, in turn, increased fecundity. This hypothesis is appealing because this selective pressure could have been present at any stage among the four hypotheses we propose for the emergence of pair-bonds in a section below.
In evolutionary psychology, an adaptation is “…an inherited and reliably developing characteristic that came into existence as a feature of a species through natural selection because it helped to directly or indirectly facilitate reproduction during the period of its evolution” ( Buss et al., 1998 , p. 535; see also Williams, 2019 ). This approach is based, rightly, on the difficulty of testing hypotheses about the adaptive benefits of traits in ancestral environments. There is an equally valid approach, however, adopted by behavioral ecologists, that views current utility of adaptations as evidence that can be extrapolated to the past ( Fox and Westneat, 2010 ). One definition that has arisen from this approach is that “[a]n adaptation is a phenotypic variant that results in the highest fitness among a specified set of variants in a given environment” ( Reeve and Sherman, 1993 , p. 9).
Taken together, these two approaches to adaptation support the view that romantic love is a “complex suite of adaptations” ( Buss, 2019 , p. 42). The numerous mechanisms recruited in romantic love, the large number of psychological characteristics, and the multiple functions it serves suggest that romantic love may be an amalgamation of numerous adaptations that respond to a variety of adaptive challenges. However, while romantic love may comprise several inter-related adaptations, this does not preclude the possibility that some components are by-products. A by-product is a trait that evolved “not because it was selectively advantageous, but because it was inextricably linked…to another trait that was reproductively advantageous” ( Andrews et al., 2002 , p. 48).
Health-promoting benefits of romantic love, such as elevated mood, increased sleep quality, and up-regulated immune responses, for example, may be by-products of mood circuitry (see Nettle and Bateson, 2012 ; D’Acquisto, 2017 ; Jahangard et al., 2017 ) or other mechanisms, even though they offer some survival or reproductive advantage. Elevated mood, better sleep quality, and an associated up-regulated immune system probably evolved prior to the emergence of romantic love (see Flajnik and Kasahara, 2010 ; Loonen and Ivanova, 2015 ). As a result, it might be prudent to contend that romantic love is a complex suite of adaptations and by-products.
Further, while the evidence points to romantic love as a suite of adaptations and by-products, it is not adaptive in every context. Romantic love continues to have its reproduction-promoting functions in the modern world in some circumstances, either by immediately promoting reproduction, or indirectly promoting reproduction via the formation of romantic relationships, the members of which later reproduce. To that extent, romantic love is sometimes adaptive (see Laland and Brown, 2011 , for distinction between “adaptation” and “adaptive” and lists of benefits, above, for examples of how romantic love can be adaptive). There are circumstances when romantic love may be maladaptive, however, as is evidenced by the substantial fitness-relevant costs of romantic love detailed above. Cogent examples of this are when a loved one is already in a committed relationship or otherwise not interested, when an individual engages in obsessive pursuit that can have social or even legal ramifications, or when violence ensues.
When applied to romantic love, the fourth of Tinbergen’s (1963) four questions asks, “What is the evolutionary history of romantic love?” Phylogenetic explanations focus on the origin and maintenance of a trait in historical evolutionary terms ( Tinbergen, 1963 ; Bateson and Laland, 2013 ). They put a biological trait in a comparative perspective by focusing on the presence or absence of the trait in closely, and sometimes more distantly, related species. In this section, we describe the theory of independent emotion systems and articulate a theory of co-opting mother-infant bonding mechanisms. We examine the primitive structures related to romantic love that arose in our mammalian evolutionary past and were restructured in pair-bonded species. We also examine the particular history of pair-bonds, and thus romantic love, in hominin evolution, with a comparison to other species of primates, especially apes. Finally, we examine the effect of gene-cultural evolutionary issues with regard to romantic love.
Fisher’s ( 1998 , 2000 , see also Fisher et al., 2002 ) evolutionary theory of independent emotions systems delineates sex drive (lust), attraction (romantic love), and attachment (pair-bonds). Sex drive is primarily associated with estrogens and androgens and serves to motivate individuals to engage in sexual activity, generally. Attraction is primarily associated with the catecholamines (i.e., dopamine and norepinephrine), phenylethylamine, and serotonin and serves to focus efforts on preferred mating partners. Attachment is primarily associated with oxytocin and vasopressin and serves to enable individuals to engage in positive social behaviors and connections of a sufficient length of time to satisfy species-specific parenting approaches ( Fisher, 1998 ). Sex drive relates most to the sex function of romantic love, attraction to the mate choice and courtship functions, and attachment to the pair-bonding function. Romantic love shares similarities with the ‘courtship attraction system’ found in many mammals ( Fisher et al., 2006 ).
While the theory of independent emotion systems ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ) has been the predominate theoretical account of the evolution of romantic love for more 20 years, comparative studies, imaging studies, and assessments of psychological characteristics have raised the possibility of a complimentary evolutionary theory, that of co-opting mother-infant bonding mechanisms. Literature on romantic love, maternal love (of which mother-infant bonding is a part), mother–infant bonding, and pair-bonding ( Bartels and Zeki, 2004 ; Ortigue et al., 2010 ; Numan and Young, 2016 ; Walum and Young, 2018 ) suggests romantic love may have evolved by co-opting mother-infant bonding mechanisms. Co-option is an evolutionary process whereby a trait (e.g., mechanism, morphology, behavior) is repurposed – that is, it serves a different function to that which it originally served (see McLennan, 2008 ).
Animal research, focusing on mammals, and involving, monogamous prairie voles, finds substantial similarities between mother-infant bonding mechanisms and pair-bonding mechanisms ( Numan and Young, 2016 ). “[A]mygdala and nucleus accumbens–ventral pallidum (NA–VP) circuits are involved in both types of bond formation, and dopamine and oxytocin actions within NA appear to promote the synaptic plasticity that allows either infant or mating partner stimuli to persistently activate NA–VP attraction circuits, leading to an enduring social attraction and bonding” ( Numan and Young, 2016 , p. 98). Some of these circuits do not appear to be involved in human romantic love, but there are other similarities that support a theory of co-opting mother-infant bonding in humans.
Several brain regions implicated in romantic love overlap precisely with that involved in maternal love. This includes activity in numerous regions that are associated with a high density of oxytocin and vasopressin receptors ( Bartels and Zeki, 2000 , 2004 ) although it should be noted that in the study that asserts this, participants included mothers experiencing maternal love beyond the mother-infant bonding stage. A meta-analysis of love also found romantic and maternal love shared activity in dopamine-rich areas ( Ortigue et al., 2010 ). Almost nothing is known about the mechanisms regulating the infant side of mother-infant bonding. However, some inferences have been made from animal models which suggest that the mechanisms may be similar to those regulating the maternal side, but without involvement of the amygdala (see Sullivan et al., 2011 , for review).
There are substantial psychological similarities between romantic love and early parental love, of which mother–infant bonding is a part. Extreme similarities exist between romantic love and early parental love in the domains of altered mental state, longing for reciprocity, idealization of the other, and dichotomous resolution of the establishment of intimate mutually satisfying reciprocal patterns of interaction usually marked by a culturally defined ritual ( Leckman and Mayes, 1999 ). Similar trajectories of preoccupation in romantic love and parental love also exist. In romantic love, preoccupation increases through the courtship phase and peaks at the point of reciprocity where preoccupation begins to slowly diminish. In parental love, preoccupation increases throughout pregnancy and peaks at the point of birth where preoccupation begins to diminish.
Romantic love in humans is caused by physiological mechanisms whose evolutionary roots were planted in our early mammalian ancestors. These evolutionary roots provided the raw materials that were fleshed out, in evolutionary time, to form the basis of a wide range of social behaviors in mammals, including those related to sex drive, mate choice, and attachment ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ; Broad et al., 2006 ; Carter and Perkeybile, 2018 ; Curley and Keverne, 2005 ; Fisher et al., 2006 ; Fischer et al., 2019 ; Johnson and Young, 2015 ; Numan and Young, 2016 ; Porges, 1998 ). Romantic love may have evolved after the neural circuitry associated with mate choice became populated by oxytocin receptors which played a role in the evolution of enduring social attraction and pair-bond formation (see Numan and Young, 2016 ). “[P]air bonding is the evolutionary antecedent of romantic love and…the pair bond is an essential element of romantic love” ( Walum and Young, 2018 , p. 12).
Examining the similarities between the neurobiological and endocrinological mechanisms involved in mother-infant bonding and pair-bonding in mammals, it becomes apparent that the maternal functions of this suite of adaptations arose deep in the evolutionary history of mammals ( Numan and Young, 2016 ). Their derived, pair-bonding functions would have arisen later in a very small number of species (only 3–5% pair-bond). As such, the neural circuitry and other proximate mechanisms involved in mother-infant bonding in mammals “may have provided a primordial neural scaffold upon which other types of strong social bonds, such as pair bonds, have been built” ( Numan and Young, 2016 , p. 99). We are, thus, on reasonably solid ground to posit evolutionary trajectories of romantic love. Figure 1 presents information and hypotheses about the evolutionary history of romantic love. Evolutionary trajectories of romantic love start with the ancestral mammalian mother–infant bonding mechanisms and culminate in their co-option and modification for pair-bonding in several mammalian lineages ( Numan and Young, 2016 ). Human romantic love results from one of these trajectories. In another trajectory—the one that includes pair-bonding prairie voles ( Microtus ochrogaster )—we know quite a lot about the functioning of oxytocin, vasopressin, and dopamine in facilitating pair-bonding (e.g., Carter and Getz, 1993 ; Carter and Perkeybile, 2018 ; Walum and Young, 2018 ). Although these derived changes to the primitive mammalian machinery may not be the direct evolutionary antecedents of those at work in humans (they are, rather, the product of parallel evolution), they provide a window into how basic machinery can be modified to affect those ends. One substantive difference appears to be the relative importance of the hormonal drivers in the smaller species, and the dopamine-related ones in humans ( Broad et al., 2006 ; Fisher et al., 2016 ).
Phylogenetic relationships among select mammal species that pair-bond.
Humans are members of the primate superfamily Anthropoidea, amongst whom there is great diversity in social systems, and whose ancestral state likely included complex group-based social relationships ( Kay et al., 1997 ; Shultz and Dunbar, 2007 ). This would have included long-term association between unrelated males and females—which is a far cry from the solitary system that is modal and ancestral for mammals ( Lukas and Clutton-Brock, 2013 ; Opie et al., 2013 ). There are even some members of this lineage who have evolved pair-bonds, such as the marmosets and tamarins (Callitrichidae), and gibbons (Hylobatidae). The similarities between these species and humans in terms of the adaptive suite related to pair-bonds, like the similarities between humans and voles, are due to convergent/parallel evolution ( French et al., 2018 ).
Our closest living relatives are the common chimpanzee ( Pan troglodytes ) and bonobo ( Pan paniscus ) with whom we share a common ancestor just 5–8 million years ago. While bonobos are alluring due to their free-willed sexual nature, common chimpanzees provide a better glimpse into the behavior of our direct ancestors. Although the common chimpanzee mating system is defined as promiscuous, there are, in fact, three forms of common chimpanzee mating tactics ( Morin, 1993 ). The first two—possessive mating and consortships—involve some of the characteristics we associate with romantic love, such as a more-than-fleeting association and mate guarding, but they are much rarer than the third type, opportunistic mating. The comparison of chimpanzees and humans, thus, suggests that one possible hypothesis for the emergence of romantic love is that it originated in their common ancestor (H1 in Figure 1 ). Alternatively, it might be that the common ancestor had an adaptive repertoire that was primed for its emergence when the requisite socioecological context arose. In this way, the evolution of romantic love from chimp-like mating is similar to the evolution of human culture from chimp-like culture.
For some, the origin of romantic love was more likely to have fallen somewhere on our side of the human–chimpanzee split (e.g., Fisher et al., 2016 ). Even so, we are left with the difficulty of pinpointing exactly when it arose—attributable to there being only one extant hominin species from amongst the many that have existed ( Pigliucci and Kaplan, 2006 ) and the lack of direct fossil evidence for romantic love. If we accept the conventional view that romantic love evolved to facilitate pair-bonding, then we can search for clues about the evolution of the former by tracing the evolution of the latter ( Fletcher et al., 2015 ). A transition from ape-like to human-like sexual behavior in our lineage may have pre-dated the emergence of the genus Homo ( Lovejoy, 1981 )—and, thus, we have a second hypothesis (H2 in Figure 1 ). A comparison of sexual dimorphism in Australopithecus and early genus Homo , however, suggests a third hypothesis—that it arose after their emergence (H3 in Figure 1 ). Several lines of evidence suggest that the earliest members of our species, Homo sapiens , pair-bonded but were not necessarily monogamous. Based on an examination of the distribution of mating systems in modern, small-scale human societies and three correlates of primate mating systems ( Dixson, 2009 ), it is possible to conclude that pair-bonds are a “ubiquitous” feature of human mating that can manifest through polygyny or polyandry, but most commonly occur in the form of serial monogamy ( Schacht and Kramer, 2019 ). The final hypothesis, thus, is that romantic love is the unique domain of our species (H4 in Figure 1 ).
The transition to mostly monogamous and some polygynous groupings could have had a transitional phase where polygynous groupings were the norm ( Chapais, 2008 , 2013 ). Pair-bonds may have arisen from a complex interaction between the fitness benefits and costs of mating and parental care ( Quinlan, 2008 ). The transition from ape-like promiscuity to human pair-bonds may have been driven by the provision of females by low-ranking males ( Gavrilets, 2012 ). The direct benefits for females was the food provided, for the males, the mating opportunity. This may have led to selection for males that were less aggressive and more prosocial. The female mate-choice mechanism is a distinct possibility for explaining human self-domestication ( Gleeson and Kushnick, 2018 ).
Romantic love is a universal or near-universal feature in human societies ( Jankowiak and Fischer, 1992 ; Gottschall and Nordlund, 2006 ; Jankowiak and Paladino, 2008 ; Fletcher et al., 2015 ; Buss, 2019 ; Sorokowski et al., 2020 ). A small number of genetic correlation studies show that there are a number of genes associated with romantic love ( Emanuele et al., 2007 ; Murray et al., 2019 ; Acevedo et al., 2020 ). Other insights into the genetic evolution of romantic love can be garnered from elsewhere, however. For example, life history theory provides insight into ethnic or geographical variation in romantic love and its role in providing sexual access by women.
Romantic love is among the most common reasons female adolescents give for having sex ( Ozer et al., 2003 ). A “slow” life history strategy is associated with eros more than other loving styles ( Marzec and Łukasik, 2017 ). Psychopathology associated with impulsivity is a feature of a “fast” life history strategy, as is promiscuous sexuality ( Del Giudice, 2016 ). Greater impulsivity is associated with a reduced likelihood of giving romantic love as a reason for having sex among adolescent females ( Dawson et al., 2008 ).
As a result, genetic determinants of life history strategies (e.g., Figueredo et al., 2004 ) may influence the occurrence of romantic love. National scores on the life history strategy genetic factor index correlate with adolescent fertility rates indicating that genetic predictors of a fast life history are associated with higher rates of adolescent pregnancy ( Luoto, 2019b ). This ethnic or geographical variation in the genetic determinants of life history strategies may also represent ethnic or geographic variation in the genetic determinants and reproductive relevance of romantic love.
In addition to this, cultural factors may have affected the role of romantic love in mating and marriage decisions—and this has implications for understanding the evolution of romantic love ( Fletcher et al., 2015 ). Arranged marriages are the norm in 80% of 200 forager societies from the Ethnographic Atlas ( Apostolou, 2007 ). Phylogenetic methods to reconstruct the ancestral marriage patterns of our species using the same data found that there were likely marriage transactions (brideprice or brideservice) but only a limited amount of polygyny ( Walker et al., 2011 ). While the ancestral state for arranged marriages was not definitive, arranged marriages were likely present around 50 thousand years ago, when our ancestors expanded their range beyond Africa. So, despite romantic love being viewed as an important component of marriage and mating, it may have played a role of decreasing importance in the recent evolutionary history of our species. Arranged marriages may have limited the role of female mate choice in intersexual selection ( Apostolou, 2007 ). Further, despite romantic love’s decreased role in courtship and marriage, it may have continued to serve a role in facilitating pair-bonding as romantic love can develop even in the arranged-marriage context. The role of romantic love in facilitating mate choice, courtship, and marriage may now be increasing with the decline and modification of arranged marriages in many parts of the world (e.g., Allendorf and Pandian, 2016 ). This may be the result of the increasing sexual equality of women (e.g., de Munck and Korotayev, 1999 ).
Romantic love is a complex and multifaceted aspect of human biology and psychology. Our approach in this review has been to highlight how Tinbergen’s (1963) “four questions” can help us to synthesize the important strands related to the mechanisms, development, fitness-relevant functions, and evolutionary history of this phenomenon. Here, we synthesize what this review has presented in each level of explanation and suggest what this indicates about other levels of explanation. We then highlight some gaps in our knowledge that could be filled with future research and present a new ethologically informed working definition of romantic love.
One of the benefits of using Tinbergen’s four questions as a framework to describe a complex trait such as romantic love is its ability for one level of explanation to provide insights into the other level of explanation (see Tinbergen, 1963 ; Bateson and Laland, 2013 ; Zietsch et al., 2020 ). In particular, an understanding of the proximate causes of romantic love has provided insights into the functions and phylogeny of romantic love although an understanding of the ultimate level of explanation provides some insights into the mechanisms of romantic love.
Multiple mechanistic systems involved in romantic love suggests it may serve multiple functions and may be a suite of adaptations and by-products rather than a single adaptation. We found that romantic love is associated with activity in a number of neural systems: reward and motivation, emotions, sexual desire and arousal, and social cognition. It is also associated with activity in higher-order cortical brain areas that are involved in attention, memory, mental associations, and self-representation. We also found that romantic love is associated with a number of endocrine systems: sex hormones, serotonin, dopamine, oxytocin, cortisol, and nerve growth factor. This is consistent with our position that romantic love serves mate choice, courtship, sex, and pair-bonding functions. Reward and motivation system activity may be particularly involved in the mate choice function of romantic love. Cortisol may be particularly indicative of the courtship function of romantic love, which overlaps with pair-bonding. Neural areas associated with sexual desire and arousal and the activity of sex hormones may play a particular role in the sex function. Finally, reward and motivation regions of the brain (rich with oxytocin receptors) and activity of the oxytocin system may play a particular role in the pair-bonding function of romantic love. Our understanding of the biological mechanisms that cause romantic love supports our description of romantic love’s functions.
Mechanistic similarities between romantic love and mother-infant bonding suggest that romantic love may have evolved by co-opting mother-infant bonding mechanisms. This articulates one hypothesis about the evolutionary history of romantic love that complements the predominate theory of independent emotion systems ( Fisher, 1998 , 2000 ; Fisher et al., 2002 ). This is supported by the psychological similarities between romantic love and early parental love.
Evidence of substantial activity of oxytocin receptor rich brain regions and the oxytocin endocrine system in romantic love lends weight to the position that romantic love only evolved after the neural circuitry associated with mate choice, specifically, regions of the mesolimbic reward pathway and dopamine rich areas, became populated by oxytocin receptors specifically receptive to stimuli from mating partners. That played a role in the evolution of enduring social attraction and pair-bond formation ( Numan and Young, 2016 ). This supports our claim that romantic love probably evolved in conjunction with pair-bonds in humans. As a result, we are bolstered when we contend that romantic love emerged relatively recently in the history of humans.
The duration of romantic love also raises questions about the functions of romantic love. It has been said that the psychological features of romantic love can last from 18 months to 3 years in reciprocated romantic love. However, in our evolutionary history, romantic love would have usually occurred in the context of pregnancy and child birth. Mother-infant bonding becomes active around the time of childbirth. We are not aware of any research that has investigated whether romantic love can occur at the same time as mother-infant bonding or whether it must subside for mother-infant bonding to become active. Answering this question would elucidate if the functions of romantic love extinguish once reproduction has been successful. The existence of long-term romantic love also raises questions about the functions of romantic love. It has been posited that long-term romantic love is “part of a broad mammalian strategy for reproduction and long-term attachment” ( Acevedo et al., 2020 , p. 1). This may indicate that long-term romantic love serves similar functions to romantic love that lasts a shorter period of time.
Just as the multiple biological mechanisms involved in romantic love suggests a variety of functions, the functions of romantic love specified in our review suggests specific biological mechanisms are involved. As outlined above, specific functions may be associated with specific mechanisms and this should be an area of targeted research.
The possibility of romantic love evolving by co-opting mother-infant bonding mechanisms raises a number of possibilities in relation to the proximate causes of romantic love. It suggests that social activity associated with mother–infant bonding (e.g., filling of needs, specific cues) may be particularly important precursors to, or features of, romantic love. It suggests that many of the genes and polymorphisms involved in causing romantic love may have been present in mammals since the emergence of mother–infant bonding, making comparative animal research using mammals relevant. It also suggests that further research into shared neural activity between romantic love and mother–infant bonding is warranted.
We contend that romantic love probably emerged in conjunction with pair-bonds in humans or human ancestors. As such, further information about the similarities and differences between romantic love (pair-bonding) and companionate love (established pair-bonds) is needed. In particular, information about any role of the mesolimbic pathway (see Loth and Donaldson, 2021 ) or regions associated with sexual desire in companionate love would help to shed light on the evolutionary history of pair-bonding and pair-bonds. Specifically, this could shed light on if, as has been suggested (see Walum and Young, 2018 ), romantic love and pair-bonds are inextricably linked.
One issue with research into the mechanisms of romantic love is that it has, with some exceptions (e.g., Fisher et al., 2010 ), utilized samples of people experiencing romantic love who are in a relationship with their loved one. Romantic love serves a mate choice and courtship function, and as a result, a large proportion of people experiencing romantic love are not in a relationship with their loved one (e.g., Bringle et al., 2013 ). A small number of studies have directly investigated unrequited love (e.g., Tennov, 1979 ; Baumeister et al., 1993 ; Hill et al., 1997 ; Aron et al., 1998 ; Bringle et al., 2013 ), but none of these investigated the mechanisms that cause romantic love. Studying such people might identify the specific contributions of particular mechanisms to particular functions. For example, the mechanisms associated with the pair-bonding function of romantic love may not be active in individuals who are engaging in courtship and the mechanisms involved in courtship may not be present in lovers who are already in a relationship with their loved one. Research would benefit from considering the mechanisms that underlie related psychopathologies and it would be useful to understand the relationship between mate preferences and romantic love.
Molecular genetics research, such as that undertaken by Acevedo et al. (2020) , could further identify contributions of genes in people experiencing romantic love. Resting state fMRI provide an opportunity to investigate networks characteristic of psychopathology related to romantic love. Research should investigate the automatic/internal emotional regulatory network and the volitional/external regulatory network associated with mania/hypomania in people experiencing romantic love. Further research is required into the endocrinology of romantic love. In particular, further research is needed into the role of opioids, corticotropin-releasing factor, glutamate, acetylcholine, and vasopressin in romantic love. Efforts should be made to combine psychological and mechanisms research. For example, differences in neural or endocrine activity may be present in people experiencing romantic love who display elevated symptoms of depression compared to those who display reduced symptoms. As a result, neuroimaging and endocrinological studies could categorize people experiencing romantic love according to their levels of depression or type of hypomanic symptoms.
Given the large number of fMRI studies, interpreting the neuroimaging literature can be overwhelming. It has been nearly 10 years since the last meta-analysis of fMRI studies including romantic love. It is time for another one that focuses solely on romantic love. There is also a pressing need to attempt to replicate and extend endocrine studies and to specifically investigate the oxytocin system in people experiencing romantic love using validated measures of romantic love. As with many areas of psychological research ( Henrich et al., 2010 ), and specifically in areas related to mating psychology ( Apicella et al., 2019 ; Scelza et al., 2020 ), there is a pressing need to ensure that samples used in research are not exclusively Western, educated, industrialized, rich, and democratic.
Limited ontogeny research has elucidated the mechanisms causing romantic love across the lifespan. The literature that has (e.g., Luoto, 2019a ), has focused on mate choice, rather than romantic love, per se . We know nothing about the neurobiology or endocrinology of romantic love in children or about the endocrinology of long-term romantic love. It would be useful to investigate how the functions of romantic love differ according to age of individuals or the duration of romantic love. Internal and external factors influence romantic love, although there has been surprisingly little research into this topic. It would be prudent to continue to develop a more detailed understanding of the factors that lead to romantic love (e.g., Riela et al., 2010 , 2017 ). It would be useful to better understand the relationship between attachment styles and romantic love. Research should investigate if romantic love can occur at the same time as mother-infant bonding, or if they are mutually exclusive states.
Research into the functions of romantic love is sparse. There is a need for clear, evidence-informed definitions and descriptions of each of the functions of romantic love. It is likely that different mechanisms moderate different functions, and research should attempt to determine the contribution of specific genetic, neural, and endocrine activity to each individual function (see Zietsch et al., 2020 ). The advent of contraception and the adoption of family planning strategies means romantic love now serves more of a sex function than a pregnancy function in some environments. This is particularly the case early in a relationship. Pregnancy may become a feature as a relationship progresses and the fitness consequences of romantic love need to be investigated. Romantic love’s role as a suite of adaptations and by-products should be investigated. There is theoretical support for the notion that romantic love serves a health-promoting function (e.g., Esch and Stefano, 2005 ); however, there is a limited number of studies demonstrating a health-promoting effect of romantic love.
The relative infancy of genetic research, the lack of a clear fossil record, and the small number of species with which comparative analysis can be undertaken, means novel and creative means of investigating the phylogeny of romantic love must be undertaken. There is a need to pin-point the phylogenetic emergence of romantic love and the factors that caused it. To do this, more research into the genetics of romantic love must be conducted, and this should consider the phylogeny of specific genes and polymorphisms (e.g., Acevedo et al., 2020 ; see also Walum and Young, 2018 ). Efforts to assess the contribution of sexual selection to the evolution of romantic love are warranted. Studies of newly discovered fossils can help to identify shifts in sexual dimorphism that are indicative of pair-bonds. Further observational and experimental research into romantic love in hunter-gatherer tribes could tell us more about how romantic love functioned in our evolutionary history. Comparative research still has much to contribute. Research should explore the possibility that initial changes to the ancestral mammalian physiology that led directly to human romantic love arose in response to selection on both mating and non-mating-related behavior, such as pro-sociality (e.g., Barron and Hare, 2020 ; Luoto, 2020 ) or unique aspects of our species’ parenting repertoire. It might be fruitful to further investigate the relationship between romantic love and life history theory (e.g., Olderbak and Figueredo, 2009 ; Marzec and Łukasik, 2017 ). Finally, efforts should be made to elaborate and test the theory that romantic love emerged by co-opting mother–infant bonding mechanisms.
The introduction to this review provided four definitions or descriptions of romantic love. For decades, most definitions ( Hendrick and Hendrick, 1986 ; Sternberg, 1986 ; Hatfield and Rapson, 1993 ) of romantic love have informed research into the cognitive, emotional, and behavioral characteristics of romantic love. The past two decades, however, have seen an increasing focus on the biology of romantic love. Only recently has an evolution-informed definition been proposed ( Fletcher et al., 2015 ). That working definition, however, does not incorporate much of the research that provides insight into the proximate and ultimate causes of romantic love.
We believe that the analytical approach taken in this review has identified sufficient information to justify the development of a new ethologically informed working definition of romantic love. The purpose would be to create an inclusive definition that is useful for researchers in varied disciplines investigating romantic love’s psychological characteristics, genetics, neurobiology, endocrinology, development, fitness-relevant functions, and evolutionary history. It may also be of use to psychologists and psychiatrists attempting to understand the experience and etiology of romantic love in their practice. It should be sufficiently precise and descriptive to both guide and link research. We provide, here, a working definition of romantic love:
We situate the study of romantic love within the context of existing human mating literature. Our definition recognizes that romantic love is experienced across the lifetime of an individual, that research has shed light on the social, psychological, genetic, neural, and endocrine characteristics associated with it, and that it occurs in both sexes. Our definition also recognizes that romantic love serves a variety of functions and that these functions may vary across the lifespan. It does not exclude long-term or unrequited romantic love from the definition. Health is not identified as a function of romantic love in our definition despite being considered in our review. If more evidence comes to light, this definition can be amended to incorporate health.
Our definition has similarities and differences with the definition proposed by Fletcher et al. (2015) . This is appropriate given both are informed by evolutionary approaches which differ somewhat. We do not specifically define romantic love as being a commitment device or reference passion, intimacy, and caregiving. In our review, we recognize that romantic love is a commitment device and serves to display commitment and signal fidelity as part of its courtship function. We believe that reference to romantic love’s behavioral activity and courtship and pair-bonding functions sufficiently encapsulate this concept. Sternberg’s (1997) definition of romantic love and Fletcher et al.’s (2015) definition include references to passion and intimacy. Caregiving (e.g., provision of psychological and emotional resources, sharing resources), while associated with pair-bonding, is not sufficiently definitive of romantic love using Tinbergen’s four questions as a framework to include in our definition.
We do not reference the universality of romantic love. While some experts assert its universality (e.g., Fletcher et al., 2015 ; Buss, 2019 ), we believe that the finding of Jankowiak and Fischer (1992) leaves enough uncertainty for it to be prudent to omit this aspect from our definition. Their research has found no evidence of romantic love in fifteen cultures (see Jankowiak and Paladino, 2008 , for update to the original investigation) although this is probably the result of lack of data rather than evidence to the contrary. Once this matter is settled, which could be achieved by further investigating those societies where no evidence of romantic love was found, the definition can be amended. Fletcher et al. (2015) state that romantic love is associated with pair-bonds. We do the same by stating that pair-bonding is one of the functions of romantic love.
We also do not make specific reference to romantic love suppressing the search for mates. We recognize this as a cost in our review, but do not believe that this is so definitive of romantic love to include in our definition. Rather, we believe that our reference to “behavioral” activity and the “mate choice” function of romantic love in our definition sufficiently accommodates this feature. Our definition provides more detail than that provided by Fletcher et al. (2015) by including elements derived from substantial research into the mechanisms, ontogeny, functions, and phylogeny of romantic love. Like the Fletcher et al. (2015) definition, our definition recognizes that romantic love has distinct psychological characteristics and that we know about some of the proximate mechanisms that regulate it. However, as explained above, we do not include reference to the health-promoting effects of romantic love.
As more information about romantic love is gathered, we anticipate the definition to develop. However, we believe that this definition is an improvement upon previous definitions and adequately captures what is currently known about romantic love’s proximate and ultimate causes. It would be useful for researchers investigating romantic love from myriad perspectives. This definition should be critiqued and improved, and we welcome any such efforts from researchers and theorists across the spectrum of academic disciplines.
Our review provides a comprehensive account of the phenomenon known as romantic love. It covers topics such as social precipitants, psychology, genetics, neurobiology, and endocrinology. It provides an account of romantic love across the lifetime of an individual and is the first to propose four discrete reproduction-related functions of romantic love supported in the literature: mate choice, courtship, sex, and pair-bonding. It provides a summary of the benefits and costs of romantic love, outlines possible selective pressures, and posits that it is a complex suite of adaptations and by-products. We propose four potential evolutionary histories of romantic love and introduce the theory of co-opting mother-infant bonding mechanisms. We have identified a number of specific and general areas for future research. Our review suggests a new, ethologically informed working definition of romantic love that synthesizes a broad range of research. The working definition we propose serves to define a complex trait in a way that can both guide and link research from a variety of fields.
AB conceived the manuscript. AB and GK collaborated on the development of the analytical framework and writing of the manuscript. Both authors approved the final version.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We would like to thank the reviewers for comments that helped to improve the manuscript.
The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpsyg.2021.573123/full#supplementary-material
Love is everywhere you look. People talk about love in pop songs, on TV, across social media, over dinner, at work, and in school hallways. There is also growing scientific interest in romantic love, as is evident from the increased number of publications on this topic, the organization of conferences—and the Greater Good Science Center’s new project on the science of love, which launches this month.
Why? First, romantic love pertains to virtually everyone. More than 80% of American adolescents reported to have been involved in at least one romantic relationship by the age of 18, according to one 2003 study , and love has been observed in almost all cultures that have been studied . Second, when people fall in love, it greatly affects their lives . People are sometimes even willing to change their friends, job, country, or religion to be with their beloved.
But do we really understand love? Unfortunately, there are many misconceptions about romantic love permeating popular media, the scientific community, or both. Some of these stem from the assumptions we make about romantic love. Others arise from hypotheses or interpretations put forth in scientific articles being cited in other articles as empirical evidence. Collectively, these misconceptions hamper the progress of the scientific understanding of romantic love—and they can lead any of us astray when we think about love in our own lives. Here are six misconceptions about romantic love that are not supported by the research to date.
The first misconception is that romantic love is something that must exist between two people. For example, an anonymous reviewer of one of my manuscripts commented, “It’s odd that ~1/6 of the sample who were purportedly ‘in love’ were not in a relationship with the target of their love.”
Contrary to what the reviewer seemed to think, it does not take two to love. While romantic love has obvious interpersonal aspects (i.e., people are in love with another person and romantic relationships involve more than one person by definition), romantic love is not necessarily dyadic or interpersonal. For example, people can develop love feelings for someone before they become involved in a romantic relationship—and they can still experience love feelings after a relationship has ended. People can be in love with someone who doesn’t love them back. People can love someone they have never been and will never be in a romantic relationship with. People can experience love feelings for someone they have never even interacted with. Examples of this are love at first sight and parasocial attachment to celebrities or fictional characters in movies, TV shows, video games, and books.
So, romantic love is not always a social process and does happen outside of relationships. The misconception that romantic love only happens within relationships has led some people to confuse relationship satisfaction and love feelings. But people can be satisfied with a relationship if it fulfills some need (such as money, housekeeping, sex, protection, child care, status, personal growth), even if they don’t love their partner. And in abusive relationships, it is possible that the victim loves their abuser while being unsatisfied with the relationship. So, relationship satisfaction is not the same as how in love someone is.
Many of us believe love is an emotion, like fear, anger, sadness, surprise, disgust, and joy.
Although scientists do not agree on how many and which types of love exist, they do agree that there are multiple types of love—and that’s actually one reason to assume that love as a whole is not an emotion. For example, researchers have distinguished between infatuation (aka passionate love) and attachment (aka companionate love). Infatuation is the early stage of love that is associated with euphoria, nervousness, and butterflies in the stomach. Attachment, on the other hand, takes time to develop and is a calming, comforting feeling.
There are also reasons to assume that the different types of love themselves are not emotions either. First, love elicits various emotions depending on the situation. Loving someone who loves you back can make you experience the emotion joy, while loving someone who does not love you back can make you experience the emotion sadness.
There’s another reason why the different types of love are not really emotions: My own neuroscience research finds that distraction after a romantic breakup decreased negative feelings but not the intensity of love, and that negative reappraisal of an ex-partner (e.g., “They weren’t so great”) decreased love intensity yet increased negative feelings.
Those observations suggest that love regulation and emotion regulation are distinct. In other words, love regulation targets love feelings (such as infatuation and attachment), whereas emotion regulation targets emotions (such as fear, anger, sadness, surprise, disgust, and joy).
Finally, love can be very long-lasting, whereas emotions are usually quite fleeting. Research has shown that emotions typically last for a half hour up to several days. The longest-lasting emotion was sadness, which can last two to five days. In contrast, it is not uncommon for infatuation to last for weeks or months and for attachment to last for years or decades.
Rather than an emotion, scientists have called love an attitude, a script, or a motivation or drive—like craving, lust, hunger, and thirst.
The third misconception is that romantic love has mainly positive effects.
Of course, love has many positive effects on people and society. Infatuation, for example, elicits positive emotions such as euphoria, and romantic relationships increase happiness and life satisfaction. But it is often overlooked that love has many negative effects on people and society, as well.
First, love can elicit several negative emotions. Infatuation is stressful, love can be accompanied by jealousy, the death of a romantic partner may elicit intense grief, and unreciprocated love and romantic breakups trigger sadness and shame.
Second, love can reduce general well-being. Romantic breakups are a main risk factor for depression in adolescents. And dysfunctional romantic relationships and romantic breakups are associated with decreased happiness and life satisfaction.
Third, people who are in love may be distracted from their duties (such as work or homework) because they think about their beloved all the time. Even though this may not bother the infatuated person, it may result in a loss of productivity or at least frustration in the people around the lover.
Fourth, love plays a role in several mental disorders (such as sexual dysfunctions, paraphilic disorders, and erotomanic and jealous delusional disorders), as well as in suicidal behavior. Finally, love is associated with criminal behavior such as stalking, domestic violence, and homicide.
It may be clear that love has both positive and negative effects, the latter of which cause substantial individual, social, and economic burden. I hope that scientific research on romantic love can both increase the positive effects of love and decrease its negative effects on people and society.
It’s important to know that each brain region, neurotransmitter, and hormone has multiple functions—and also that each function requires multiple brain regions, neurotransmitters, and hormones. Love affects behavior, feelings, thoughts, and bodily responses in many different ways. And each of these “symptoms” of romantic love depends on different brain regions, and multiple neurotransmitters and hormones.
Take, for example, the fact that people have better memory for information that has to do with their beloved, which is related to how arousing this information is. We know that better memory for exciting information depends on two brain regions called the amygdala and the hippocampus, the neurotransmitter noradrenaline, and the hormones adrenaline and cortisol. Therefore, it can be expected that those parts of our nervous systems are involved in the better memory for information related to the beloved.
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Or consider this: We get clammy hands when we are infatuated. Researchers know that this sweating is part of the flight-or-fight response and involves release of the neurotransmitter acetylcholine in the sympathetic nervous system, which in turn is controlled by the hypothalamus in the brain. Therefore, that brain region and neurotransmitter likely play a role in getting clammy hands when infatuated.
Even though scientists typically understand that there is no dedicated love component in our nervous systems, they could improve the focus of their research questions and designs by understanding romantic love as an emergent process that consists of numerous moving parts, each with its own neurobiological basis. But why should everyone else care? Because, perhaps, if you share this understanding of love feelings as complex neurological processes, you might better understand why love can feel so complicated to you!
There is a misconception that we will soon be able to the develop a love drug, which is something that people have pursued for ages, for example through sorcery. Even nowadays, people across the world wishfully use aphrodisiacs and love philters. Although evidence-based pharmacological manipulation of love feelings may be possible at some point, several issues prevent the development of an effective and safe “love pill” in the short term.
We are only just starting to learn which neurotransmitters and hormones might play a role in the different types of love. For example, several neuroimaging studies have shown that certain brain regions (such as the caudate, putamen, ventral tegmental area, insula, cingulate cortex, and inferior frontal gyrus) are more active when people view pictures of their beloved than when they view pictures of other people. Some of those brain regions (especially the caudate, putamen, and ventral tegmental area) contain a lot of the neurotransmitter dopamine. The activation of these dopaminergic brain regions in response to the beloved has been taken to mean that romantic love is associated with high levels of dopamine. However, it is important to note that the method used in those neuroimaging studies (functional magnetic resonance imaging) only shows what areas of the brain receive extra oxygen through blood. But this method cannot show whether dopamine is released.
As far as I know, there is only one study that has actually measured dopamine levels when people view pictures of their beloved (compared to when they view pictures of friends), using a method called positron emission tomography. That study shows more dopamine release when people view the beloved (as opposed to the friend) in two brain regions that are called the medial orbitofrontal cortex and the prefrontal cortex. This study surprisingly did not find more dopamine release when people viewed the beloved than the friend in the more typical dopaminergic regions that received more oxygen through blood in previous studies. So, more research is needed on whether and where dopamine is released when people see their beloved.
As another example, it has been suggested that romantic love is associated with low levels of serotonin because of its resemblance with obsessive-compulsive disorder. But in one study, women who were in love had higher serotonin levels in their blood than women who were not in love. And obsessive thinking about the beloved in these women was associated with higher, rather than lower, serotonin levels in their blood. So we cannot conclude at this time that romantic love is associated with low serotonin levels.
Crucially, to develop a “love pill” we would have to prove that changing the level of some neurotransmitter or hormone actually changes the intensity of love. But most studies so far have only compared people who are in love when they view pictures of their beloved with when they view other pictures. It would be informative, but more difficult, to compare people who are in love with people who are not in love. Or, even better, to compare people before and after they fall in love.
It would also be challenging to design a drug that changes love feelings for one person specifically, which would be desirable in at least some situations. For example, someone who is married might want to decrease their love feelings for a crush without changing (or while increasing) their love for their spouse. And because the neurotransmitters and hormones involved in love have many different functions, any love drug that affects the levels of these neurotransmitters or hormones may have side effects that could be adverse. So, unfortunately, it will be a while until you can use a love drug to change how in love you are, if ever.
However, there are many situations in which it might be beneficial to change how in love you are—and my research says that you can. The solution is not drugs, but rather intentional thinking.
In some situations, love feelings may be stronger than desired, such as when people are still in love with an ex-partner, when the love is forbidden, and when people are in love with someone who treats them poorly. In situations like those, people may want to decrease how in love they are, which can help them cope with heartbreak. It can also help people to stop pursuing an inappropriate partner or to put an end to a dysfunctional (e.g., abusive) relationship.
At other times, love feelings may be weaker than desired, such as when they decline over time in long-term relationships. In situations like that one, you may want to increase how in love you are, which could help you maintain long-term relationships.
Nevertheless, many people think that love regulation is difficult or even impossible. But my research suggests that people can become more or less in love by doing or thinking certain things. One study shows that something as simple as looking at pictures of the beloved increases infatuation and attachment. Another study finds that thinking about positive aspects of the beloved (“they are so smart,” “he is such a good cook”), the relationship (“we agree on how to spend our money”), and the future (“we’ll live happily ever after”) increases attachment. And yet another of my studies suggests that fantasizing about having sex with your beloved (such as imagining something you would like your partner to do to you during sex) increases sexual desire and infatuation. These are strategies that you can use to strengthen your love feelings for someone.
In another experiment, thinking about the negative aspects of the beloved (“she never puts the cap on the toothpaste”), the relationship (“we fight a lot”), and the future (“we won’t stay together forever”) decreased infatuation and attachment. These are strategies that you can use to weaken your love feelings for someone.
So, in contrast to what you may think, it is beneficial and possible to change how in love you are. Give it a try when you find yourself more or less in love than you’d like to be!
This article is a shortened and revised version of “ Refuting Six Misconceptions About Romantic Love ,” published in May 2024 by the journal Behavioral Sciences .
Sandra Langeslag, Ph.D. , is an associate professor in the Department of Psychological Sciences at the University of Missouri–St. Louis. She is the director of the Neurocognition of Emotion and Motivation (NEM) Lab. Her research focuses mainly on the interaction between romantic love and cognition.
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Published on January 11, 2019 by Shona McCombes . Revised on August 15, 2023 by Eoghan Ryan.
A thesis statement is a sentence that sums up the central point of your paper or essay . It usually comes near the end of your introduction .
Your thesis will look a bit different depending on the type of essay you’re writing. But the thesis statement should always clearly state the main idea you want to get across. Everything else in your essay should relate back to this idea.
You can write your thesis statement by following four simple steps:
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What is a thesis statement, placement of the thesis statement, step 1: start with a question, step 2: write your initial answer, step 3: develop your answer, step 4: refine your thesis statement, types of thesis statements, other interesting articles, frequently asked questions about thesis statements.
A thesis statement summarizes the central points of your essay. It is a signpost telling the reader what the essay will argue and why.
The best thesis statements are:
The thesis statement generally appears at the end of your essay introduction or research paper introduction .
The spread of the internet has had a world-changing effect, not least on the world of education. The use of the internet in academic contexts and among young people more generally is hotly debated. For many who did not grow up with this technology, its effects seem alarming and potentially harmful. This concern, while understandable, is misguided. The negatives of internet use are outweighed by its many benefits for education: the internet facilitates easier access to information, exposure to different perspectives, and a flexible learning environment for both students and teachers.
You should come up with an initial thesis, sometimes called a working thesis , early in the writing process . As soon as you’ve decided on your essay topic , you need to work out what you want to say about it—a clear thesis will give your essay direction and structure.
You might already have a question in your assignment, but if not, try to come up with your own. What would you like to find out or decide about your topic?
For example, you might ask:
After some initial research, you can formulate a tentative answer to this question. At this stage it can be simple, and it should guide the research process and writing process .
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Now you need to consider why this is your answer and how you will convince your reader to agree with you. As you read more about your topic and begin writing, your answer should get more detailed.
In your essay about the internet and education, the thesis states your position and sketches out the key arguments you’ll use to support it.
The negatives of internet use are outweighed by its many benefits for education because it facilitates easier access to information.
In your essay about braille, the thesis statement summarizes the key historical development that you’ll explain.
The invention of braille in the 19th century transformed the lives of blind people, allowing them to participate more actively in public life.
A strong thesis statement should tell the reader:
The final thesis statement doesn’t just state your position, but summarizes your overall argument or the entire topic you’re going to explain. To strengthen a weak thesis statement, it can help to consider the broader context of your topic.
These examples are more specific and show that you’ll explore your topic in depth.
Your thesis statement should match the goals of your essay, which vary depending on the type of essay you’re writing:
If you want to know more about AI tools , college essays , or fallacies make sure to check out some of our other articles with explanations and examples or go directly to our tools!
College essays
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A thesis statement is a sentence that sums up the central point of your paper or essay . Everything else you write should relate to this key idea.
The thesis statement is essential in any academic essay or research paper for two main reasons:
Without a clear thesis statement, an essay can end up rambling and unfocused, leaving your reader unsure of exactly what you want to say.
Follow these four steps to come up with a thesis statement :
The thesis statement should be placed at the end of your essay introduction .
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College essays that worked and how yours can too.
CAMBRIDGE, MASSACHUSETTS - JULY 08: A view of Harvard Yard on the campus of Harvard University on ... [+] July 08, 2020 in Cambridge, Massachusetts. Harvard and Massachusetts Institute of Technology have sued the Trump administration for its decision to strip international college students of their visas if all of their courses are held online. (Photo by Maddie Meyer/Getty Images)
The college essay is a pivotal piece of the college application showcasing your individuality and differentiated outlook to admissions officers. What makes an essay truly shine? Let’s dive into the words behind three standout essays highlighted by university websites and a school newspaper's brand studio so you can get into the right mindset for crafting your own narrative.
Essay Excerpt: ‘Bra Shopping ’ (Harvard)
Featured by the Harvard Crimson Brand Studio , Orlee's essay recounts a student's humorous and insightful experience of bra shopping with her grandmother, weaving in her unique family dynamics and challenges at her prestigious school.
What Works:
For Your Essay : To write an essay that embraces your uniqueness, start by identifying a quirky or challenging experience that reflects who a key insight into your experience. Think about how this experience has shaped your perspective and character. Use humor and honesty to bring your story to life, and focus on how you have embraced your differences to become stronger and more resilient.
Best 5% interest savings accounts of 2024, finding connections: humor and self-reflection.
Essay: ‘Brood X Cicadas ’ (Hamilton College)
As an example on Hamilton's admissions website, Nicholas writes about the cicadas swarming his hometown every 17 years and draws a parallel between their emergence and his own transition to college life. He uses humor and self-reflection to create a relatable and engaging narrative.
For Your Essay: To infuse humor and self-reflection into your essay, start by identifying an ordinary experience or object and think about how it relates to your life. Write down funny or insightful observations about this connection. Use humor to make your essay more engaging, but ensure it still conveys meaningful self-reflection. This balance can make your essay both entertaining and profound.
Essay: ‘ Facing The Hot Griddle ’ (Johns Hopkins University)
In this essay published by Hopkins Insider, Rocio uses the process of making tortillas to explore her multicultural identity and the challenges she has faced. Her story beautifully weaves together her Guatemalan heritage and her experiences growing up in the United States.
For Your Essay: To write an essay that explores your identity through a metaphor, start by thinking about an activity or tradition that holds significant meaning for you. Consider how this activity relates to your life experiences and personal growth. Use detailed descriptions to bring the activity to life and draw connections between the process and your own journey. Reflect on the lessons you've learned and how they've shaped your identity.
A winning college essay isn’t simply about parading your best accomplishment or dramatizing your challenges. It’s not a contest for which student is the most original or entertaining. Rather, the essay is a chance for you to showcase your authenticity, passion, resilience, social awareness, and intellectual vitality . By sharing genuine stories and insights, you can create an essay that resonates with admissions committees and highlights your unique qualities.
For you to have the best possible essay, mindset is key. Here’s how to get into the zone:
The secret to a standout college essay lies in its authenticity, depth, and emotional resonance. By learning from these successful examples and getting into the right mindset, you can craft an essay that not only stands out but also provides a meaningful insight into who you are. Remember, your essay is your story—make it a piece of writing that you will always be proud of.
The Windmill at Wijk bij Duurstede ( c 1668-1670) by Jacob Isaacksz van Ruisdael. Courtesy the Rijksmuseum, Amsterdam
Windmills were once just machines on the land but now seem delightfully bucolic. could wind turbines win us over too.
by Stephen Case + BIO
Today’s modern wind turbines seem to repel poetic or artistic engagement. It is difficult to imagine a landscape painter portraying their spare lines and uniform rows as icons of a pastoral idyll, as the windmills of the past often were.
Perceptions of modern wind turbines seem worlds away, for example, from how Robert Louis Stevenson described the windmills of England in 1882:
There are, indeed, few merrier spectacles than that of many windmills bickering together in a fresh breeze over a woody country, their halting alacrity of movement, their pleasant business, making bread all day, with uncouth gesticulations, their air gigantically human, as of a creature half alive, put a spirit of romance into the tamest landscape.
The aspects that struck Stevenson – the motion of windmills, symbols of prosperity, on the horizon – were highlighted a decade before by the French novelist Alphonse Daudet in his depiction of Provençal life:
The hills all about the village were dotted with windmills. Whichever way you looked, you could see sails turning in the mistral above the pines, and long strings of little donkeys laden with sacks going up and down the paths; and all week long it was a joy to hear on these hill-tops the cracking of whips, the creaking of the canvas of the sails, and the shouts of the millers’ men … These windmills, you see, were not only the wealth of our land, they were its pride and joy.
Yet perceptions of windmills have not been uniformly idyllic. Since they first appeared on the landscape of medieval Europe, windmills represented an imposition of the technological on the pastoral. They were, in the phrase of the wind energy author Paul Gipe, ‘machines in the garden’, straddling the boundary of the agrarian and mechanical. Unlike the static technologies shaping landscapes – from cathedral towers or canals in the past, to power lines, solar panels or rows of genetically modified crops today – windmills are constantly in motion. They refuse to passively disappear into the landscape.
With the spread of modern windfarms, the cultural positioning of wind power remains a contentious issue. But the debate is not new: for centuries, the symbolic nature of windmills – as technological monsters or icons of the idyllic – has been open to question. Understanding this debate can help open new avenues for engagement with today’s wind technology.
T hough European windmills first appeared as early as the 11th or 12th centuries, there are still clues to how this new technology was initially perceived. In Dante’s Inferno , for instance, when the poet reaches the deepest circle of hell, Satan becomes visible through the gloom. As the ominous figure appears, he is described with a metaphor that would have been growing familiar to many of Dante’s original 14th-century readers:
As, when thick fog upon the landscape lies, or when the night darkens our hemisphere, a turning windmill seems afar to rise …
Through the darkness, the devil’s huge limbs are visible like the sails of a windmill pinwheeling on the horizon. To readers whose largest built realities were stable, unmoving church towers or city walls, the ceaseless, arching sweep of a windmill’s arms was no doubt disconcerting to say the least. Later, when Cervantes pictured them as giants in Don Quixote’s imagination, he could gesture to this lingering unease over this most prominent structure on the medieval horizon.
Windmills became integral to communities: structures with names, histories and inhabitants
Besides their visual impression, the first windmills also challenged existing energy infrastructure. Since Roman times, power to mill grain had been confined to water mills and remained the property and protected prerogative of feudal landowners. As the first windmills spread throughout England, they were greeted with resistance by landowners attempting to preserve their ancient rights. Windmills ‘threatened both lucrative old water mill franchises and traditional upper-class privileges,’ recounts the historian Edward Kealey in Harvesting the Air (1987), and ‘offered quick-witted peasants an opportunity to evade manorial regulations, act independently, and become quite prosperous.’ Angry landowners ordered illegal windmills be torn down.
A Windmill near Brighton (1824) by John Constable. Courtesy the V&A Museum, London
Yet eventually this disrupting, disquieting technology became an aspect of the pastoral ideal. Windmills became integral to communities: structures with names, histories and inhabitants. Operating a windmill took skill, care and attention. The miller, who lived in the windmill, was fully occupied with watching the weather, trimming the sails, and keeping the windmill functional from generation to generation – besides providing a vital agricultural role in the community by grinding grain. Ultimately, as the art historian Alison McNeil Kettering has argued , windmills took on the role of ‘cultural signifier’, representing provision and guardianship over a well-run community, becoming familiar icons of ‘pastoral tranquility’ and ‘agrarian idyll’.
As the last generation of millers cared for the last windmills turning in England, their aesthetic value lingered even as their commercial value disappeared. As Stanley Freese wrote in Windmills and Millwrighting (1957):
[N]either photograph nor drawing can capture for my pages the most beautiful of all country scenes; only those who have caught sight of the big white sails of a windmill following one another against a background of dark hills or woodlands, or black canvas sails soaring one after another into an evening sky, can fully apprehend the characteristic beauty of this structure, which differs from all others because it is alive with comely motion, never awkward or ungainly, but blending well with every kind of landscape.
A s steam replaced wind in Europe, a new type of windmill emerged across the Atlantic. Whereas European windmills were inhabited structures positioned within the community, the unsettled expanse of the western United States saw the windmill altered to run for decades in isolation, pumping water for farmsteads or for cattle stations scattered across hundreds of miles of arid ranchland. Dozens of models represented a Darwinian response to this environmental challenge: self-lubricating mechanisms, designed to track and spill the wind with counterweights and springs, their complex down-gearing transforming rotary motion into a steady back-and-forth pumping action in even the lightest breeze. By 1889, there were more than 70 windmill factories in cities across the American Midwest. At the European windmill’s peak, there were perhaps 100,000 of the structures across Europe; by contrast, there would eventually be more than 6 million windmills in the US.
Lame Deer, Montana, September 1941. Photo by Marion Post Wolcott, Library of Congress
Unlike the graceful European windmill, the new US variety was considered ugly and ungainly. An American architect insisted that American windmills ‘should be condemned’ as offensive to sight: ‘To see these awkward, spider-like structures dancing fandangos before our eyes disturbs the repose and mars the landscape of our otherwise beautiful homes.’ Worse, another author said the countryside was littered with wrecked windmills, casualties of the failure to maintain or lubricate – this last chore a near-weekly requirement for some of the earliest models. Yet despite these initial impressions, the new American windmill (technically, a wind pump) soon became an icon of the Western settlers themselves: independent, self-reliant, steadily facing whatever storms arose.
Manufacturers helped cultivate this view of windmills as totems of the American west
A Kansas City Star reporter writing in 1964 captured the feeling of growing up in the shadow of a farmhouse windmill, an experience common to generations of settlers and their descendants. There was :
the gentle sough of the breeze through the fan, the creak of the tower and the rhythmic metallic working of the gears and sucker rod, and finally the steady soft pouring of water into the tank … And then there was a sound all its own: a blade bent by some long forgotten encounter with the wooden tower at each revolution – thump, thump, thump, when the wind was soft and at a machine-gun rattle when a summer storm sent up dust and dead tumble weeds racing across the flat … On quiet nights, for a child awakening in the darkness of a stuffy room, the chipping of the wounded blade against the tower took on a comforting sound, reassuring that this was home, that there was no storm, and that the windmill was pumping water.
Like the European windmill before it, the American windmill was becoming a cultural signifier of a new pastoral ideal.
Courtesy the Library of Congress
In the new commercial context, windmill manufacturers helped cultivate this view of windmills as totems of the American west, presenting them in advertisements and catalogues as part of an idyllic farm landscape. Competition among manufacturers also meant windmill designs became as simple and reliant as possible. Windmills needed to be shipped across the country, assembled hundreds of miles away on the open prairie, and to operate in isolation for years on end. Their buyers needed to own, understand, and service the windmills themselves. The success of this approach is evidenced by the windmills still spinning across the US and the world, with a handful of companies today producing designs that remain unchanged from the 1910s. Like the European windmill, American windmills became pastoral icons, their ceaseless labour – working in the slightest breeze and weathering the harshest storm – a visual metaphor for diligence, independence and patient endeavour.
T oday’s massive wind turbines are larger than past windmills by an order of magnitude. The question facing this latest generation of wind technology is more than whether they will be seen as icons of energy independence and sustainability, or simply another extractive industry ‘replicating the exploitative practices of the infrastructures they would replace,’ as the historian of science Nathan Kapoor put it . Rather, the question is whether the social imaginaries available to previous generations of windmills – the chance to become symbols of provision, community or self-reliance – are available to modern windfarms. It is a question playing out, for instance, in debates between farmers who welcome wind turbines and the income they represent and those – often within the turbines’ shadow – who see them as monstrous technological impositions on the landscape.
What prevents modern wind turbines from the sort of cultural integration that European and American windmills obtained? Part of the answer comes by considering wind technologies in light of work by the philosopher of technology Albert Borgmann. In his classic Technology and the Character of Contemporary Life (1984), Borgmann offers his analysis of ‘device’ as both critique and exemplar of modern technology. According to Jesse S Tatum, a device is a technological artefact designed to make ‘a single commodity highly available while making the mechanism of its procurement recede from view’. Our current technological paradigm is the creation of as many devices as possible, from cars to electronics to infrastructure, to make commodities hyper-convenient and abundant.
The problem with devices is that, by design, they are black boxes. Devices, in Borgmann’s treatment, are inaccessible to understanding or engagement. They demand no skill, disburdening their users while, in Borgmann’s words, resisting ‘appropriation through care, repair, the exercise of skill, and bodily engagement’. Devices, whether kitchen appliances or the electrical systems that supply their energy, neither express their creator nor ‘reveal a region and its particular orientation within nature and culture.’ Writing in 1984, long before the advent of smartphones, Borgmann’s analysis is prescient in highlighting how technological devices provide essential commodities such as information, entertainment, energy and food, while simultaneously keeping the means of their production inaccessible and largely invisible.
Impossible to consume the commodity of ground grain from a windmill without ‘invoking or enacting a context’
Despite the abundance of commodities, our interaction with devices leaves us distracted and dissatisfied as our engagement with the world is reduced to ‘narrow points of contact in labour and consumption’. For Borgmann, the solution is not a return to a pretechnological setting but rather to recentre human practices and flourishing around what he refers to as ‘focal things’. In contrast to a device, a focal thing is ‘inseparable from its context, namely, its world, and from our commerce with the thing and its world, namely, engagement’. Focal things represent locality and craft; they engage body and mind, and that engagement requires skill: ‘The experience of a thing is always and also a bodily and social engagement with the thing’s world.’
Focal things invite users to interact with them, giving rise to what Borgmann calls ‘focal practices’ that make the thing part of the broader culture and social structure of the community. The European windmill, dependent in its operation on the skill and care of the miller, in its construction and maintenance on the knowledge and expertise of carpenters and millwrights, and in its purpose on local agricultural practices, was a quintessential Borgmannian focal thing – a nexus of material culture, social heritage and artistic expression. It was impossible to simply consume the commodity of ground grain from a windmill without ‘invoking or enacting a context’.
Likewise, American windmills, though factory manufactured on a large scale, immediately entered the context of homestead or ranch. They were designed to be open and accessible to users for care and maintenance, and the farmer or rancher took ownership and exercised skill in that maintenance and care – learning the idiosyncrasies of each individual windmill. While providing the essential commodity of water, windmills took on additional symbolic and cultural roles, offering a sense of solace, wellbeing and aesthetic pleasure (as evidenced by their reappearance on smaller scales as lawn ornaments across the Midwest and beyond). Both European and American windmills, according to Borgmann’s paradigm, functioned as focal things – technological artefacts that connected their users and communities to both landscape and wind.
M odern wind turbines are designed to fit the device paradigm, providing the commodity of energy or (to the landowner who rents space for their footprint) money, but they fail in a vital respect. No matter how they are isolated from nearby communities or coastlines, their motion keeps them visible on the horizon, even as the other large-scale energy infrastructure devices (electric lines, telescope poles, cellphone towers) fade from view. Their primary mechanism of transforming wind into energy remains impossible to hide. As the growth of sustainable energy continues, more and larger windfarms will be required, and their visible impact will only increase. The tension between wind turbines as disengaging devices and their obvious presence on the landscape will continue. Previous iterations of windmills, however, were not ultimately accepted by making them invisible but rather by changing how they were perceived. Can something similar happen for modern wind turbines, transforming them from devices to something that’s closer to Borgmann’s focal things, and opening a path to richer cultural and aesthetic engagement?
Wind turbines are currently designed and implemented as devices. At least in part for safety and liability concerns, they are isolated even as they remain in view. Wind turbines are, like Borgmann described high-rise buildings, ‘though imposing … not accessible either to one’s understanding or to one’s engagement.’ But this disengagement is one of the main reasons wind turbines are often viewed with such negativity. As the philosopher Gordon G Brittan Jr expresses it, wind turbines ‘are ubiquitously and anonymously the same, alien objects impressed on a region but in no deep way connected to it. They have nothing to say to us, nothing to express; they conceal rather than reveal.’
On the other hand, these modern windmills have many characteristics of Borgmann’s focal things. Focal things, according to Borgmann, ‘are concrete, tangible, and deep … They engage us in the fullness of our capacities. And they thrive in a technological setting.’ By depth, Borgmann means that all of an object’s physical features are significant, something acutely true of precision-designed wind turbines constructed so that each curve and angle generates as little resistance and as much efficiency as possible. Depth means complexity, and complexity can be an aspect of engagement. Yet much of the complex, elegant design of wind turbines that could make them engaging rather than alien remains physically hidden and corporately protected.
An unused turbine blade propped along a country road allows one to experience its scale and scope
Engagement with focal things need not be physical. Besides the handful of skilled workers who design, construct and maintain the turbines (and whose work itself is a point of possible wider engagement, as shown by the reality TV show Turbine Cowboys ), most people will not be able to physically engage with these artefacts in any practical way. But education and outreach are powerful forms of engagement largely unutilised by the various actors involved in the creation and maintenance of windfarms. This makes sense within the device paradigm: we aren’t usually invited into engagement with our electrical substations. But if it is impossible to ignore them, education and engagement can help us move toward making wind turbines focal things.
Other avenues of engagement could be as simple as suggested routes navigating drivers or cyclists on public roads through wind farms, allowing visitors to intentionally experience them as part of an aesthetic vista. And though no one should be climbing them, there are ways to bring their physicality nearer the observer. Near my own home, for instance, an unused turbine blade propped lengthwise along a country road allows one to experience a sense of the scale and scope of these artefacts. The experience of locality could be integrated with education: information such as how fast the turbines spin or how much energy they generate from moment to moment need not be obscured or accessible only to experts. These physicalities could instead be ways to engage those passing through. This doesn’t mean expensive interpretive centres at each wind farm (though it could); it might be as simple as signage along the roadway. Science communicators can help here to form bridges between the artefacts and the curious public who watches them along the horizon.
Though a more complicated concern, ownership needs to be considered as well. A deep sense of engagement comes about from artefacts that are individually or communally owned. It was this sense of ownership that allowed US windmills their cultural role and that made European windmills a vital part of their communities. This continues today, as individuals and local communities lovingly restore and maintain these earlier windmill iterations, though they are no longer the means of providing the commodities they once did. The current model of off-site ownership of wind turbines is a powerful factor keeping today’s windmills firmly within the device paradigm.
For Borgmann, ‘the dignity and greatness of a thing in its own right’ – and the stately turning turbines along my Midwestern horizons can certainly have this dignity – is what allows focal things and the practices built around them to ‘gather and illuminate the tangible world and our appropriation of it’.
Borgmann’s device paradigm helps make sense of cultural and aesthetic concerns around modern wind farms, and the history of windmills gives hints of how things might be different. Without efforts of engagement, wind turbines remain inscrutable devices, easy to reduce to uniform, monolithic symbols of extractive capitalism. Unless we try to integrate them into local culture as focal things, they will never be symbols of the landscape like windmills of the past.
Global history
The route to progress
Anticolonial modernity was founded upon the fight for liberation from communists, capitalists and imperialists alike
Frank Gerits
Philosophy of mind
The problem of erring animals
Three medieval thinkers struggled to explain how animals could make mistakes – and uncovered the nature of nonhuman minds
The disruption nexus
Moments of crisis, such as our own, are great opportunities for historic change, but only under highly specific conditions
Roman Krznaric
History of science
His radiant formula
Stephen Hawking’s greatest legacy – a simple little equation now 50 years old – revealed a shocking aspect of black holes
Roger Highfield
What is intelligent life?
Our human minds hold us back from truly understanding the many brilliant ways that other creatures solve their problems
Abigail Desmond & Michael Haslam
Pleasure and pain
Eulogy for silence
Tinnitus is like a constant scream inside my head, depriving me of what I formerly treasured: the moments of serene quiet
Diego Ramírez Martín del Campo
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True Love: The Power of Love. 1 page / 633 words. Introduction Love is an elusive yet omnipresent force, often described as the most profound of human emotions. It transcends cultural, social, and economic boundaries, resonating deeply within the human experience. The concept of true love, in particular, is celebrated in literature, music, and ...
The concept of love: an exploratory study with a. sample of young Brazilians. 1. Thiago de Almeida, José Fernando Bittencourt Lo mônaco. Department of Psychology of Learning, Development and ...
The concept of true love is based on the belief that to truly love someone you have to accept them for who they are (including their shortcoming and faults), put their happiness above your own (even if your heart is broken in the process) and that you will always love them even if they are not by your side. In essence it is a self-sacrificing ...
Figure 1. Description: (A) Presence of love (all factors are present).(B) Absence of love (state of non-love or state where all factors are latent or dormant).(C) Different levels of love due to variations in the four factors.(D) Movement from non-love toward love (developmental stage: at least one but not all four factors are present).(E) Movement away from love toward non-love (decline stage ...
The essays focus on the contradictions and limits of love, manifested in such phenomena as trust, abuse, grief, death, violence, politics, and desire. An erudite examination of the many facets of love, this book fills a lacuna in the philosophy of this richly complicated topic.
The cognitive, emotional, and behavioral features of romantic love result from neural activity associated with reward and motivation, emotions, sexual desire and arousal, and social cognition as well as endocrine activity associated with sex hormones, serotonin, dopamine, oxytocin, cortisol, and nerve growth factor.
Video (online) Consult the top 50 dissertations / theses for your research on the topic 'Romantic love.'. Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard ...
Love is everywhere you look. People talk about love in pop songs, on TV, across social media, over dinner, at work, and in school hallways. There is also growing scientific interest in romantic love, as is evident from the increased number of publications on this topic, the organization of conferences—and the Greater Good Science Center's new project on the science of love, which launches ...
Step 1: Start with a question. You should come up with an initial thesis, sometimes called a working thesis, early in the writing process. As soon as you've decided on your essay topic, you need to work out what you want to say about it—a clear thesis will give your essay direction and structure.
Humor and Honesty: The student's humor makes the essay enjoyable to read, while her honesty about her challenges adds depth. Self-Awareness: She demonstrates a strong sense of self-awareness ...
is a historian of science at Olivet Nazarene University in Illinois and the director of the university honours programme. He is the author of Making Stars Physical: The Astronomy of Sir John Herschel (2018), and co-editor of The Cambridge Companion to John Herschel (2024). Today's modern wind ...
"All my love, thanks for coming," Olivia wrote, alongside her signature. The young fan, Lorenza Sofrá, has an economics and business degree, and her thesis is titled "Navigating the Modern ...