In a matter of 20 seconds detection of whether a stranger is genetically inclined to being trustworthy, kind or compassionate is possible, claim researchers.
In the study, 23 romantic couples were videotaped while one of the partners described a time of suffering in their lives. The other half of the couple and their physical, non-verbal reactions were the focal point of the study.
Groups of complete strangers viewed the videos. The observers were asked to rate the person on traits such as how kind, trustworthy, and caring they thought the person was, based on just 20 seconds of silent video.
"Our findings suggest even slight genetic variation may have tangible impact on people's behaviour, and that these behavioural differences are quickly noticed by others," said Aleksandr Kogan, a postdoctoral fellow at the University of Toronto and the study's lead author.
The study builds on previous research conducted by Sarina Rodrigues Saturn, an assistant professor of psychology at Oregon State University.
In that study, Saturn and her colleagues linked a genetic variation that affects hormone/neurotransmitter oxytocin's receptor to empathy and stress reactivity.
Before the videos were recorded, the scientists tested the couples and identified their genotype as GG, AG, or AA.
Individuals homozygous for the G allele (carrying two copies of the G version of the gene) of the oxytocin receptor tend to be more "prosocial," defined by researchers as the ability to behave in a way that benefits another person.
In contrast, the carriers of the A version of the gene (AG or AA genotypes) tend to have a higher risk of autism, as well as self-reported lower levels of positive emotions, empathy and parental sensitivity.
The people carrying an A version of the gene were viewed as less kind, trustworthy and caring toward their partners in the video.
What is not known, however, is what occurs from the genetic level to the behaviour - that is, the exact way the gene affects the biology underlying behaviour is still poorly understood and remains a major topic of inquiry.
The study appeared in the latest issue of Proceedings of the National Academy of Sciences (PNAS).