People with a certain gene trait are known to be more kind and caring than people without it, and strangers can quickly tell the difference, according to US research published on Monday.
Scientists at Oregon State University devised an experiment in which 23 couples, whose genotypes were known to researchers but not observers, were filmed.
One member of the couple was asked to tell the other about a time of suffering in his or her life. Observers were asked to watch the listener for 20 seconds, with the sound turned off.
In most cases, the observers were able to tell which of the listeners had the "kindness gene" and which ones did not, said the findings in the Proceedings of the National Academy of Sciences edition of November 14.
"Our findings suggest even slight genetic variation may have tangible impact on people's behavior, and that these behavioral differences are quickly noticed by others," said lead author Aleksandr Kogan, a postdoctoral fellow at the University of Toronto.