TUESDAY, Nov. 15 (HealthDay News) -- New research suggests that a variation in a single human gene affects how other people see you at first glance in terms of your compassion, kindness and trustworthiness.

The variation might directly influence your personality, especially in terms of empathy. Or it's possible that it's connected to something else that affects the way you act. On the other hand, the research is based on only a few subjects, so much more study is needed, experts say.

Still, the findings may "speak to the power of little genetic differences to predict tangible differences in the way we behave," said study author Aleksandr Kogan, a postdoctoral fellow in psychology at the University of Toronto.

Over the past five to seven years, researchers have been exploring how genetics affect emotions, Kogan said. "What we're learning is that, to a certain extent, we have a genetic basis that supports a lot of the processes that make us nice."

In particular, researchers have focused on a hormone called oxytocin, which has been linked to emotions like love and trust and is found in a variety of animals. Higher levels of oxytocin have been linked to higher levels of trustworthiness, empathy and willingness to sacrifice, Kogan said.

In the new study, Kogan and colleagues focused on a gene linked to the brain's oxytocin receptor, which is a kind of catcher's glove that receives the hormone. They wanted to see if they could link variations in the gene to the way that people are perceived by others.

The researchers compiled 20-second, silent videos of people listening as their romantic partners told a story about a moment of suffering in the partner's life. Then they showed the videos to 116 subjects and asked them to gauge the compassion, kindness and trustworthiness of the people in the videos, Kogan said.

The researchers then tried to see if patterns in the genetic makeup of the people in the videos predicted how the subjects viewed them.

Those who were considered to be most trustworthy were similar genetically in terms of the single gene. The same was true for those who were deemed least trustworthy -- they were similar to one another, but in a different way.

People with the "kindness" gene showed more empathetic behaviors, like nodding their heads, smiling and making eye contact than people with the other type of gene.

The question now is: If these links aren't a coincidence, how are genes affecting how empathetic people appear to be to others? Could it affect their behavior? The way their faces look? Something else?

In the big picture, the research could lead to better understanding of why some people are kind and others aren't, Kogan said. It could even lead to insight into why some people are psychopaths.

Paul Zak, a brain researcher and founding director of the Center for Neuroeconomics Studies at Claremont Graduate University, in California, said the research is interesting but not yet world-changing.

"Some people would say there is now a gene for being nice to other people. That's not true at all," he said. Many other genes matter, too, he said, as do more important factors like your current physical state and your personal history.

In other words, if you're a jerk or a saint, your genes shouldn't get all the credit -- or blame.

The study appears online in this week's issue of the Proceedings of the National Academy of Sciences.

More information

The U.S. National Library of Medicine has more about genes.