Love has always been an integral part of human society, constant in its presence and unchanging in its complexity. From Romeo and Juliet to Paris and Helen of Troy, legends of great romances have enthralled humanity for thousands of years, and throughout all that time, the question is continuously asked: what is love, and why do we humans experience it? As neuroscience and psychology continue to progress, we as a species get closer to fully understanding the mechanisms and evolutionary significance behind this powerful emotion.
A Magnetic Relationship
Romantic love is almost universal. It should come as no surprise then that scientists have been carefully studying what goes on in our brains when we feel butterflies for someone! In 2006, one group of scientists decided to examine love through functional magnetic resonance imaging (fMRI). They observed how the brains of 17 people lit up through the fMRI when they were shown images of their beloved. In these cases, the brainstem’s right ventral tegmental area (VTA) and right postero-dorsal body of the caudate nucleus were activated. The VTA is the part of the brain responsible for our ‘reward system.’ It is associated with pleasure, general arousal, focused attention, and motivation to pursue rewards.
So far, so good for the love birds. But the study also looked at the brain activity of 15 people who had just been rejected. Interestingly enough, in these cases the reward system associated with gambling lit up, as well as areas of the lateral orbitofrontal cortex. The latter is associated with obsessive/compulsive behaviours and controlling anger. This fits in well with the idea that rejected lovers initially protest, rage, and then resign themselves to the outcome. While people don’t usually like talking about their breakups, the research did have some words of solace when it came to love: ‘romantic love is [also] involuntary, difficult to control, and generally impermanent.’
It’s all about chemistry
While human courtship is arguably more complex than that of animals, the behaviour of prairie voles (a type of rodent) does offer insights into our own biology. With prairie voles, females are stimulated by the release of a hormone known as oxytocin in the brain during mating. The release of oxytocin leads to attachment. In fact, if her brain is infused with oxytocin, she will become rapidly attached to the nearest male. Interestingly enough, the hormone interacts with the reward and reinforcement system driven by dopamine. This is the same ‘circuitry’ that nicotine and cocaine act on in humans to produce euphoria and addiction. Similar patterns are seen in people when looking at photographs of their lovers.
Oxytocin isn’t only related to sex. It allows prairie voles (and humans) to develop long-term attachment to an individual. This could be an attachment between mother and child, but it could also result in romantic attachment. While pair bonding utilises similar brain circuitry in male and female prairie voles, in the case of males the process is slightly different. With males, vasopressin (another hormone) stimulates pair bonding, as well as aggression towards potential rivals. Vasopressin acts upon the receptor gene AVPR1A, coded by the gene AVPR1A.
In human men, the AVPR1A gene can affect how likely they are to pair bond and the quality of their relationships. In fact, a recent study showed that men with a particular AVPR1A variant are twice as likely as men without it to remain unmarried or when married, twice as likely to report a recent crisis in their marriage. Spouses of men with the variant also express more dissatisfaction in their relationships than do those of men without it.
Sex on the brain
Satisfying relationships have consistently featured as an aspect that makes humans’ lives meaningful. However, while researchers have shown that supportive and close relationships promote health and well-being, studies on sexuality have been strikingly absent (according to a 2018 article). Sexuality is arguably a key factor that distinguishes romantic relationships from other types of close relationships.
There is more to sex than physical pleasure. One group of researchers in 2018 wanted to explore the role intimacy had on sex and orgasm (for this study, researchers defined intimacy as the experience of strong feelings of closeness, connectedness, and bonding). The study found that higher levels of intimacy are associated with higher sexual desire, which also increases the likelihood of sex to occur between partners. It was also found that couples were more likely to enjoy sex following an increase in intimacy. Who would have guessed that being emotionally intimate with your partner could lead to better sex?
So, is love an evolutionary advancement that pumps feel-good chemicals into our brains to aid in the survival of our species? Well maybe it started out that way, but love has grown into something far bigger than that in human society. Love is a feeling that is universally sought after, regardless of whether the union results in children and regardless of sexuality or gender. Even though it’s never perfect and may end in heartbreak, we continuously search to find meaningful relationships that will bring excitement and happiness into our lives. Throughout human history, one sentiment rings true: love is the most perplexing and irrational feeling yet one of the greatest pleasures humans have in their short lifetimes.
Fisher, H. E., Aron, A., & Brown, L. L. (2006). Romantic love: a mammalian brain system for mate choice. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 361(1476), 2173–2186. https://doi.org/10.1098/rstb.2006.1938
Impett, E. A., & Muise, A. (2018). The sexing of relationship science: Impetus for the special issue on sex and relationships. Journal of Social and Personal Relationships, 35(4), 433–439. https://doi.org/10.1177/0265407517752277
van Lankveld, J., Jacobs, N., Thewissen, V., Dewitte, M., & Verboon, P. (2018). The associations of intimacy and sexuality in daily life: Temporal dynamics and gender effects within romantic relationships. Journal of Social and Personal Relationships, 35(4), 557–576. https://doi.org/10.1177/0265407517743076
Young, Larry. (2009). Being Human: Love: Neuroscience reveals all. Nature. 457. 148. 10.1038/457148a.
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