Dec. 20, 2010— -- When a car cuts in traffic, what makes some drivers shrug their shoulders and others fume with road rage, bashing the horn or worse?
Scientists say it's the "warrior gene," a controversial name for a genetic variation that research has shown to have an ugly side tied to violence, risk taking and aggression.
Found in one-in-three western men, it is literally a shorter, less active version of a gene allele on the X chromosome known as Monoaminine oxidrase A gene.
"In many, many studies it appears implicated in behaviors that look like they're related to physical aggression or some kind of conduct disorder," said Rose McDermott, a political scientist at Brown and Harvard universities, told ABC News.
McDermott repeated one of her own experiments, with minor variations, for a National Geographic documentary, "Born to Rage," which will air on Tuesday, Dec. 21 at 6 p.m. ET.
In the experiment, McDermott tested men whom she knew from previous testing either had the gene variant or did not. Some of the men were mixed martial arts fighters, others former gang members and also one Buddhist monk.
They had all been told that they could take home real money after performing a vocabulary test. One man, who was actually a hired actor, annoyed the group with ridiculous questions. He was a real jerk. Later, it was revealed that he had taken half of the money the participants had earned.