After only 20 seconds, complete strangers can pick up on a person's trustworthy genes through their behavior, shows a new study. A single genetic change makes a person more compassionate and kind to others.

The gene in question is the receptor for the “love hormone” oxytocin. 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.

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 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.

"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. "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."