Strangers can "see" a persons trustworthy genes through their behaviors, suggests a new study finding that a single genetic change makes a person seem more compassionate and kind to others.

The gene in question is the "love hormone," or oxytocin, receptor. A single change in the receptor can result in higher or lower empathy, or how much you can emotionally relate to others. These changes can be detected by strangers from just 20 seconds of soundless video; these strangers could literally see the person's genes manifesting in their behavior.

Our genes are made of bases, called nucleotides, which come in four types: A, T, C, and G. Researchers have found that switching out a single A to a G on the "love hormone" receptor can have profound effects on behavior. A person with two copies of this A-to-G mutation (one from each parent) report having more empathy.

"Previous research has found that people that are GGs are more empathic, more compassionate," study researcher Aleksandr Kogan at the University of Toronto told LiveScience. These studies were self-reported by the GGs, so Kogan's study asked: "Do other people actually find people with a GG more trustworthy?"

'Thin slices' of personality

The researchers used taped conversations between long-term partners discussing a nonromantic time of personal suffering. Twenty-second clips (what researchers call "thin slices") of the most intense parts of the conversations were selected, their audio was removed and they were shown to a group of participants. The watchers were asked to rate the listener's social intelligence, their empathy, based on the quick clip.

These scores were matched up with actual counts of how many social gestures were used in the video and also the video subject's oxytocin receptor variant, or whether they had two copies of the G-type receptor gene, two copies of the A or one of both gene variation. The participants judged as less empathetic those people with either two As (AA) or GA than people with two Gs (GG). Video analysis showed that people with at least one A variant also showed fewer "pro-social" gestures, like smiling or touching their partner. [11 Effects of Oxytocin]

"The people on the video that had the copies of the G genes were treated as more compassionate, trustworthy and kind. There were specific behaviors that the G genes were doing that the A genes were doing less," Kogan said. "These behaviors were signaling to the complete strangers that this is a trustworthy person. This is speaking to the power of very slight genetic variation and the amazing human ability to pick up on the differences."

The 23 video clips contained 10 GGs, 10 GAs and 3 AA variants. On average, only about 15 percent of Caucasians have two A oxytocin receptor gene variants. Of the 10 most trusted people, as indicated by the 119 study participants, six were GGs and four were GAs, none were AAs. Of the 10 least trusted, nine had at least one A variant and only one was GG.

"In this research, Dr. Kogan has demonstrated something very interesting — that people can accurately 'read' genetic tendencies from thin slices of human behavior," Joni Sasaki, a researcher from the University of California, Santa Barbara, who wasn't involved in the study, told LiveScience in an email. "Any genetic information communicated to another person should have tremendous implications for the way people interact across many types of relationships, from close friends to complete strangers."

Many mysteries remain

Researchers don't know yet how this genetic variant may change the oxytocin receptor to cause these behavioral effects.

"Ultimately, with something as complex as empathy there's going to be a lot of genes involved and a lot of nongenetic factors; all of these different threads weave together to create a personality," Kogan said. "It's still pretty remarkable. Though there are so many other genes involved, this gene can still have an important impact."

Heike Tost, a researcher from the Central Institute of Mental Health in Germany who wasn't involved in the study, believes the results are exciting but agrees with Kogan that empathy is a complicated behavior regulated by more than one factor: "We as individuals don’t wear our 'social genotype' on the sleeve," she told LiveScience in an email. "One of these single variants will neither make us sick nor decide whether we act like 'saints or satans' toward fellow human beings."

This study was published today (Nov. 14) in the journal Proceedings of the National Academy of Sciences.

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