A gene that has been linked to both marital bliss and sadness may also make some of us more prone to spontaneous smiles and bursts of laughter.
For a new study, researchers looked at two versions of the gene variant known as 5-HTTLPR, and found that people with the short version were more likely to smile and laugh while looking at “Far Side” and New Yorker cartoons and humorous clips from the movie Strangers in Paradise.
Researchers videotaped the facial expressions of participants and coded them for genuine signs of amusement, such as crow’s feet around the eyes.
The study tested 336 participants in all, collecting their saliva samples to establish whether they had the long or short version of the 5-HTTLPR gene.
Overall, people with the short allele showed more authentic smiles and laughter than the long-allele cohort.
An earlier study showed that people with the short variant of 5-HTTLPR were more sensitive to the tenor of their spouse’s positive and negative emotions, suggesting that DNA is linked to marital satisfaction.
The new work, published in the journal Emotion, takes the research a step further.
“Our study provides a more complete picture of the emotional life of people with the short allele,” says lead author Claudia Haase, assistant professor of human development and social policy at Northwestern University.
“This study provides a dollop of support for the idea that positive emotions are under the same tent as negative ones, when it comes to the short allele,” says study senior author Robert Levenson, professor of psychology at the University of California, Berkeley.
“It may be that across the whole palette of human emotions, these genes turn up the gain of the amplifier. It sheds new light on an important piece of the genetic puzzle.”
Other researchers from UC Berkeley, and from UC San Francisco and University of Geneva are coauthors of the study.