Love can bring out both the best and the worst in people. Which way it turns depends on the best way to protect the relationship, say researchers studying the evolution of romantic love.
"Love is not merely sexual desire nor a unique emotion but rather a motivational drive-like state," says Arthur Aron of State University of New York at Stony Brook, whose research involves the use of fMRI brain scans in understanding love. New research, being presented today at a conference of personality and social psychologists in San Diego, CA, is shedding light into the role romantic love plays in the formation, development, and maintenance of close relationships.
The dark side of love
"From an evolutionary perspective, love binds romantic partners together for the long term and is associated with a wealth of positive relationship processes," says Jon Maner of Florida State University. Yet, love can also cause problems. "The more love one feels for one's partner, the more one has to lose if the relationship ends," he says. "It's all about protecting one's relationship."
Maner's research team set out to investigate just how love may sensitize people to relationship threats. In three experiments involving 130 people involved in long-term relationships, the researchers tested people's responses to attractive rivals. In one of the experiments, for example, they gave participants the opportunity to blast attractive rivals with painful, but non-injurous, blasts of white noise. In another, participants reviewed mock profiles for a student dating service and could then belittle attractive rivals.
To compare feelings of romantic love versus sexual attraction, researchers primed some participants in advance by having them write essays about times they had strong feelings of love for their partners and had some write either neutral essays or ones involving a time about sexual attraction to their partners. In each experiment, researchers found that people primed with feelings of love for their partner behaved more aggressively and belittled their rivals more. "This was especially the case for people who were chronically jealous and who worried about infidelity," Maner says.
"Experiencing strong feelings of love their partner made them vigilant to the potential for infidelity and led them to behave aggressively toward attractive rivals," Maner says. "Thus, while love serves an important relationship function and in that sense is a 'many-splendored thing' it can also have a dark side."
The resourceful side of love
Another recent study looking at love form an evolutionary perspective found that even when a partner chooses to say "I love you" depends on a cost-benefit analysis of the relationship and what best protects it.
Across six studies, Josh Ackerman of the MIT Sloan School of Management and his colleagues found that although people think that women are the first to confess love and feel happier when they receive such confessions, it is actually men who confess love first and feel happier. They also found that saying "I love you" makes the man in a couple feel most happy if the confession occurs before the couple has sex and makes women most happy if the confession happens after sex.
"This work shows that our intuitions are not always correct," Ackerman says. "When and why we express romantic love are guided by deep-seated motivations that are best understood in an economic framework. Love confessions are akin to economic resources that people use to negotiate evolved romantic interests." The studies were published in the June 2011 Journal of Personality and Social Psychology.
The health side of love
Researchers are also finding that love can play a critical role in the health of long-term relationships and of the couples themselves. Lisa Diamond of the University of Utah studies the multiple levels on which individuals in romantic relationships influence each others' moods and physical functioning.
Diamond's research team studied 34 co-habitating couples and tracked their health and well-being before, during, and after a four- to seven-day separation. The tracking included testing the couples' saliva for cortisol, a hormone associated with stress. Physical separations increased cortisol levels and had negative impacts on their sleep and levels of positive interactions. "During separations, only lengthy phone calls appeared to 'stand in' for contact," she says. "The findings can contribute to our emerging understanding of the processes through which longstanding romantic ties are beneficial for our health."
Explore further: Neurochemical evidence that long-lasting love is possible
A press conference on this research "Of Love and Valentines: What Evolution and Neurobiology Tells Us about Romance" takes place on Jan. 28, 2012, at the annual meeting of the Society for Personality and Social Psychology (SPSP).