‘Finite’ self-control gets ‘depleted by use’

Once the pool has dried up,we’re less likely to keep our cool the next time we’re faced with a situation that requires self-control.

However,Hedgcock’s study is the first to actually show it happening in the brain using fMRI images that scan people as they perform self-control tasks.

The images show the anterior cingulate cortex (ACC),which is the part of the brain that recognizes a situation in which self-control is needed and says,

“Heads up,there are multiple responses to this situation and some might not be good” – fires with equal intensity throughout the task.

However,the dorsolateral prefrontal cortex (DLPFC) – the part of the brain that manages self-control and says,“I really want to do the dumb thing,but I should overcome that impulse and do the smart thing” – fires with less intensity after prior exertion of self-control.

He said that loss of activity in the DLPFC might be the person’s self-control draining away. The stable activity in the ACC suggests people have no problem recognizing a temptation. Although they keep fighting,they have a harder and harder time not giving in.

The finding of this study could explain why someone who works very hard not to take seconds of lasagna at dinner winds up taking two pieces of cake at desert.

It could also modify previous thinking that considered self-control to be like a muscle. Hedgcock says his images seem to suggest that it’s like a pool that can be drained by use then replenished through time in a lower conflict environment,away from temptations that require its use.

The researchers gathered their images by placing subjects in an MRI scanner and then had them perform two self-control tasks – the first involved ignoring words that flashed on a computer screen,while the second involved choosing preferred options.

The study found the subjects had a harder time exerting self-control on the second task,a phenomenon called “regulatory depletion.”

Hedgcock said that the subjects’ DLPFCs were less active during the second self-control task,suggesting it was harder for the subjects to overcome their initial response.

He said that the study is an important step in trying to determine a clearer definition of self-control and to figure out why people do things they know aren’t good for them. 

The study will be published in January 2013 in the Journal of Consumer Psychology.