University of Zurich researchers used transcranial magnetic stimulation, a noninvasive method of inhibiting activity in parts of the brain, to “turn off” people’s ability to control their impulses. They focused on the temporoparietal junction, an area of the brain thought to play an important role in moral decisions, empathy, and other social interactions. They hope their research could help inform our understanding of addiction and self-discipline. From Scientific American:
In their study, subjects underwent 40 seconds of disruptive transcranial magnetic stimulation (TMS)—in which a magnetic coil placed near the skull produced small electric currents in the brain that inhibited activity of the posterior TPJ—then spent 30 minutes completing a task. To rule out a placebo effect, a control group received TMS in a different area of the brain. In one task, subjects made a choice between a reward (ranging between 75 and 155 Swiss francs) for themselves or one that was shared equally between themselves and another person, who ranged from their closest confidante to a stranger on the street. In another task subjects were offered an immediate reward of between zero and 160 Swiss francs or a guarantee of 160 Swiss francs after waiting three to 18 months. In a final task, subjects were instructed to take the perspective of an avatar and indicate the number of red dots on a ball that the avatar would see.
Subjects with an inhibited TPJ were less likely to share the money and were more likely to take the money up front rather than delay gratification and wait for a larger prize. They were also less able take on the perspective of the avatar, which makes sense, says Christian Ruff, a co-author of the paper and an economist at the University of Zurich. “The function of perspective-taking is essential to both of these tasks,” he says, in terms of both “thinking how someone else would feel if you give them money and also how you yourself in the future would feel with that money.”
The findings suggest that the TPJ plays an important role in perspective-taking, which (co-author Christian) Ruff describes as “a very basic social mechanism” that is essential not only for helping us figure out what other people may be thinking and feeling during social interactions but also in self-control, as we weigh the needs and desires of our current self against the needs and desires of our imagined future self.