With Valentine’s Day approaching, one might wonder what causes the phenomenon that we celebrate: love. Interestingly, love is not a totally abstract feeling or concept; it is a chemical change in the brain that is caused by attraction, which is linked to genetic attraction based on natural selection.
Leading biochemical researcher Helen Fisher of Rutgers University has divided the process of falling in love into three distinct stages. The first is lust, which is caused by testosterone (in both men and women) and estrogen in women. These hormones play a major role, specifically in female sex drives.
The second stage of “the love process” is attraction. This is called the “love-struck” phase, because it is during this stage that people can lose sleep and their appetites. The main hormones released are monoamines, including dopamine, which is the same compound released by cocaine and nicotine; serotonin, which may actually make us temporarily insane; and adrenaline, which is responsible for physiological changes commonly associated with falling in love, such as an increased heart rate and sweating.
The third and final stage of love is attachment. In a lasting relationship, this takes over from attraction. One of the main hormones released during this stage is oxytocin, which is linked to both sex and childbirth, and is thought to deepen a couple’s bond. The other main hormone is vasopressin, which is a kidney controller that ensures that the relationship lasts. It was actually discovered in prairie voles (notoriously “frisky” animals), via an experiment in which male voles were given vasopressin suppressors. The bonds these voles had with their mates, sexual and otherwise, decreased significantly.
However, none of these processes can occur without choosing a partner. Scientists are investigating evolutionary theories to better understand how we choose partners. It is widely thought that we are subconsciously assessing individual traits that we would like to pass onto children for the purpose of survival. Other scientists suggest that our ideals for a partner are created as early as age six, and are directly influenced by the people we see around us as we grow up, because much of neural development occurs during this stage.
Attractive traits based on family are not solely visible. Studies done by University of Chicago researcher Dr. Martha McClintock have shown that women prefer scents similar to those of their fathers. These scents are created partially by pheromones, which are determined by the makeup of the immune system and are discernible by most adult humans with their vomeronasal organs. Women most likely prefer these familiar scents because the pheromones subconsciously inform them that the immune systems of the men that smell like their fathers are similar and they are therefore reliably healthy.
Research from 1995 by Claus Wedekind of the University of Bern in Switzerland included the first “sweaty T-shirt test,” and found that women in that test preferred the scents of men with immune systems different from their own. Dr. McClintock’s research supports Wedekind’s idea that women internally prioritize the best traits to pass on to children, including immunity to a wider range of diseases.
All in all, love is a complicated, multifaceted, chemical and physical concept. Scientists are continuing to discover how we form crucial romantic and sexual bonds within our own species. They are using everything from lab rats (because rodents excrete pheromones similarly to humans!) to sweaty T-shirts to find out what it is about people that make other people “tick.” So this Valentine’s Day, feel free to send your special someone a card like this: