You may be genetically programmed to laugh, smile easily

A new study has revealed that some people can easily laugh or smile more than others because it's engraved in their genes.

In a new study, linking a gene to positive emotional expressions such as smiling and laughing, researchers demonstrated that people with a certain genetic variant, those with short alleles of the gene 5-HTTLPR, smiled or laughed more while watching cartoons or subtly amusing film clips than people with long alleles.

In the study, by Claudia M. Haase of Northwestern University and Ursula Beermann of the University of Geneva co-authored the study, which was conducted in the laboratories of Dacher Keltner and Robert W. Levenson at the University of California, Berkeley, the scientists looked at short and long alleles of the gene 5-HTTLPR, which is involved in the regulation of serotonin, a neurotransmitter implicated in depression and anxiety.

The data from the three experiments combined indicated that people with the short allele of 5-HTTLPR showed greater positive emotional expressions. Specifically, people with the short allele displayed greater genuine smiling and laughing than people with the long allele.

The study is published in the American Psychological Association journal Emotion.