Biological basis of love

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The theory of a biological basis of love has been explored by such biological sciences as evolutionary psychology, evolutionary biology, anthropology and neuroscience. Specific chemical substances such as oxytocin are studied in the context of their roles in producing human experiences, emotions and behaviors that are associated with love.

Evolutionary psychology

sexually transmitted diseases may cause, among other effects, permanently reduced fertility, injury to the fetus, and increase risks during childbirth. This would favor exclusive long-term relationships reducing the risk of contracting an STD.[1]

From the perspective of evolutionary psychology the experiences and behaviors associated with love can be investigated in terms of how they have been shaped by human evolution.

pygmy chimpanzee) are frequently cited in support of a cooperative past in humans.[7]

Bode and Kushnick undertook a comprehensive review of romantic love from a biological perspective in 2021.[8] They considered the psychology of romantic love, its mechanisms, development across the lifespan, functions, and evolutionary history. Based on the content of that review, they proposed a biological definition of romantic love:

Romantic love is a motivational state typically associated with a desire for long-term mating with a particular individual. It occurs across the lifespan and is associated with distinctive cognitive, emotional, behavioral, social, genetic, neural, and endocrine activity in both sexes. Throughout much of the life course, it serves mate choice, courtship, sex, and pair-bonding functions. It is a suite of adaptations and by-products that arose sometime during the recent evolutionary history of humans.[8]

Recently, Bode proposed that romantic love evolved by co-opting mother-infant bonding.[9] The theory says that the genes that regulate mother-infant bonding were recreated and took on a new function. The theory is based on a literature arising from research on prairie voles that pair bonding uses the same mechanisms that mother-infant bonding use as well as the available human evidence. The theory was used to critique a previously asserted evolutionary theory of romantic love proposed by Helen Fisher.[10] Bode's theory explains not only one process in the emergence and subsequent evolution of romantic love, but also proposed a new model of the mechanisms of romantic love. According to the model, romantic love comprises elements such as bonding attraction, attachment, obsessive thinking, sexual desire, and courtship attraction.

Social psychology

Social psychological approaches to explaining love have been developed to help further explain the psychological components involved in love. One of the more prominent concepts pertaining to love was proposed by Robert J. Sternberg known as the "Triangular theory of love". Proposed within this theory, love follows a triangular motion, flowing with combinations of different levels within the three sides of the triangle. The three sides are Intimacy, Passion, and Commitment.[11] Within those three sides of the triangle, combinations between two can produce certain types of love and affection. For example, Intimacy plus Passion leads to romantic love while Intimacy plus Commitment leads to compassionate love. The relative amount of love invested is explained by the size and general form of the triangle. Triangular theories do not solely apply to one's own current relationship, they also can be meant for explaining what different levels of intimacy/passion/commitment mean in an imbalanced triangle, or even determine your love triangle for a preference of relationship.

Neurochemistry

Simplified overview of the chemical basis of love.

There have been fewer than 45 biological studies of romantic love.

neuropeptides) that govern these drives are testosterone, estrogen, dopamine, oxytocin, and vasopressin.[13][15]

Central

paraventricular hypothalamic nucleus mediate partner preference and attachment behaviors.[13][16] Sex drive is modulated primarily by activity in the mesolimbic dopamine pathway (ventral tegmental area and nucleus accumbens).[13] Trace amines (e.g., phenethylamine and tyramine) play a critical role in regulating neuronal activity in the dopaminergic pathways of the central nervous system.[17]

Testosterone and estrogen contribute to these drives by modulating activity within dopamine pathways.[13] Adequate brain levels of testosterone seem important for both human male and female sexual behavior.[18] Norepinephrine and serotonin have a less significant, contributing role through their neuromodulatory effects upon dopamine and oxytocin release in certain pathways.[13]

The chemicals triggered that are responsible for passionate love and long-term attachment love seem to be more particular to the activities in which both persons participate rather than to the nature of the specific people involved.[14] There is mixed evidence about the role of cortisol in romantic love.[19]

A less speculative account of the neurochemistry of romantic love was provided by Bode & Kushnick in 2021.[19] While they recognize that other factors play a role, they summarize the available human endocrinological evidence that implicates testosterone, dopamine, oxytocin, serotonin, cortisol, and nerve growth factor in romantic love. There is no evidence that estrogen and norepinephrine play a major role in romantic love (although they might) and only neuroimaging and genetic evidence of vasopressin's involvement.[20][21]

Role of the limbic system

The role of the limbic system in emotion was first explained by James Papez in 1937 within his paper titled "A proposed mechanism of emotion". The model described is known as the Papez circuit. The Papez circuit highlighted the presence of neuronal pathways between the vestibular and the limbic system.

UCSF provide an overview of the scientific theories and findings relating to the role of the limbic system in love, attachment and social bonding. They advance the hypothesis that our nervous systems are not self-contained, but rather demonstrably attuned to those around us and those with whom we are most close. This empathy, which they call limbic resonance, is a capacity which we share, along with the anatomical characteristics of the limbic areas of the brain, with all other mammals.[24] Their work builds on previous studies of the importance of physical contact and affection in social and cognitive development, such as the experiments conducted by Harry Harlow
on rhesus monkeys, which first established the biological consequences of isolation.

Brain imaging

Brain scanning techniques such as functional magnetic resonance imaging have been used to investigate brain regions that seem to be involved in producing the human experience of love.[25]

In 2000, a study led by Semir Zeki and Andreas Bartels of University College London concluded that at least two areas of the brain become more active when in love. These were foci in the media insula, which the brain associates with instinct, and part of the anterior cingulate cortex, which is associated with feelings of euphoria.[26]

Ortigue et al. found that an unconscious prime of the name of a romantic partner activated similar brain regions as when subjects were consciously aware of seeing partners' faces.[27] Subliminal priming with either a beloved's name or a favorite hobby activated emotion and motivational brain regions: caudate nucleus, insula, bilateral fusiform regions, parahippocampal gyrus, right angular gyrus, occipital cortex, and cerebellum. However, the love prime evoked more activation in bilateral angular gyri and bilateral fusiform regions than the hobby prime. These regions are associated with integrating abstract representations, and the angular gyrus in particular is involved with abstract representations of the self. The authors also found a correlation (r=0.496, p=0.002) between activation of a region of the angular gyrus with a passionate-love scale measuring subjective feelings of love.[27]

Love and motivation

Conscious thoughts about a romantic partner activate brain regions related to reward and motivation. Ortigue et al. investigated whether unconscious priming by a partner's name could also affect motivation. They found that priming by either a beloved or a favorite hobby improved reaction times in identifying whether a string of letters was a word or not compared against priming by a neutral friend. The authors suggest this effect happens because a beloved's name "may call for a goal-directed state" and produce "dopaminergic-driven facilitation effects."[27] Similarly, the love one feels for their friends may also be biologically motivated. Isern-Mas and Gomila argue that while the love we feel for our friends is not romantic, it is still motivated through feelings of moral obligations as well as changes in the brain resulting from prosocial experiences.[28] The common motivation whether it be love romantically or through a non-intimate companion can be connected to positive feelings and rewards that in turn, form social bonds.[29] As seen in other animals as well, the immediate connections between the love of a mother and their infant impacts their personality as they age.[30]  Harlow described love as a secondary drive for all animals, but it is essential for proper development. The animals that were left abandoned, had trouble socializing with others and often had personality issues as well.[30] The Behavioral Activation System (BAS), which plays a role in directing behavior, is believed to play a role in romantic love.[31]

See also

References

  1. ^ The Handbook of Evolutionary Psychology, edited by David M. Buss, John Wiley & Sons, Inc., 2005. Chapter 14, Commitment, Love, and Mate Retention by Lorne Campbell B. and Bruce J. Ellis.
  2. ^ "Evolutionary psychology: the emperor's new paradigm" by D. J. Buller in Trends Cogn. Sci. (2005) Volume 9 pages 277-283.
  3. ^ The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature Archived 15 May 2007 at the Wayback Machine by Geoffrey F. Miller in Psycoloquy (2001) 12,#8.[page needed]
  4. ^ Evolution of human music through sexual selection by G. F. Miller in N. L. Wallin, B. Merker, & S. Brown (Eds.), The origins of music, MIT Press, (2000). pp. 329-360.
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    . The sex drive evolved to motivate individuals to seek a range of mating partners; attraction evolved to motivate individuals to prefer and pursue specific partners; and attachment evolved to motivate individuals to remain together long enough to complete species-specific parenting duties. These three behavioural repertoires appear to be based on brain systems that are largely distinct yet interrelated, and they interact in specific ways to orchestrate reproduction, using both hormones and monoamines. ... Animal studies indicate that elevated activity of dopaminergic pathways can stimulate a cascade of reactions, including the release of testosterone and oestrogen (Wenkstern et al. 1993; Kawashima &Takagi 1994; Ferrari & Giuliana 1995; Hull et al. 1995, 1997, 2002; Szezypka et al. 1998; Wersinger & Rissman 2000). Likewise, increasing levels of testosterone and oestrogen promote dopamine release ...This positive relationship between elevated activity of central dopamine, elevated sex steroids and elevated sexual arousal and sexual performance (Herbert 1996; Fiorino et al. 1997; Liu et al. 1998; Pfaff 2005) also occurs in humans (Walker et al. 1993; Clayton et al. 2000; Heaton 2000). ... This parental attachment system has been associated with the activity of the neuropeptides, oxytocin (OT) in the nucleus accumbens and arginine vasopressin (AVP) in the ventral pallidum ... The activities of central oxytocin and vasopressin have been associated with both partner preference and attachment behaviours, while dopaminergic pathways have been associated more specifically with partner preference.
  14. ^
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    . Recent studies also highlight remarkable anxiolytic and prosocial effects of intranasally administered OT in humans, including increased 'trust', decreased amygdala activation towards fear-inducing stimuli, improved recognition of social cues and increased gaze directed towards the eye regions of others (Kirsch et al., 2005; Kosfeld et al., 2005; Domes et al., 2006; Guastella et al., 2008).
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  29. ^ Marazziti, Donatella; Baroni, Stefano (1 February 2012). "Romantic love: the mistery of its biological roots". Clinical Neuropsychiatry. 9 (1): 14–20.
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