You talk to a friend. Then you talk to Siri on the iPhone. Does your brain function differently when interacting with a machine versus another person? According to a recent study, there might be one small brain region dedicated to dealing only with people—in order to lie to them.

Researchers had 18 subjects play poker against a variety of human and computer opponents. The participants were encouraged to bluff—they’d get money if their bluffs were successful.

Sometimes they were given a weak hand. The researchers evaluated functional MRI signals of the players’ brains. Could they tell by looking at the brain patterns whether the player was about to bluff a human?

They found that most regions of the brain that have been previously identified with social interactions lit up regardless of whether the subject was playing a person or a machine. But one small region—the temporal parietal junction, or TPJ—seemed to activate only when participants contemplated bluffing another human being.

The study was published in the journal Science. [R. McKell Carter et al., "A Distinct Role of the Temporal-parietal Junction in Predicting Socially Guided Decisions"]

Says study author Scott Huettel, “Social information may cause our brains to play by different rules than nonsocial information.” At least when it comes to deception.

—Cynthia Graber

[The above text is a transcript of this podcast.]

[Audio clip of Scott Huettel courtesy of Science/AAAS.]