New MRI images show what the brain looks like when a person runs out of patience and loses self-control. The study by University of Iowa neuroscientist William Hedgcock confirms previous studies that show self-control is a finite commodity that can be depleted by use. Hedgcock says once the pool of self-control has dried up, we're less likely to keep our cool the next time we're faced with a situation that requires self-control. Hedgcock's study is also the first to show what is happening in the brain using fMRI images that scan people as they perform self-control tasks.
The researchers say the image above shows brain activity when people exert self-control and the image below shows brain activity after people have been engaged in self-control tasks long enough that self-control resources have been depleted. The images show the anterior cingulate cortex (ACC) - the part of the brain that recognizes a situation in which self-control is needed and fires with equal intensity throughout the task. The images also show the dorsolateral prefrontal cortex (DLPFC), the part of the brain that manages self-control and fires with less intensity after prior exertion of self-control.
Hedgcock says 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.
This could help explain why someone who works very hard not to take seconds of lasagna at dinner winds up taking two pieces of cake at desert. Hedgcock says his images seem to suggest that self-control is like a pool that can be drained by use and then replenished through time in a lower conflict environment.
The researchers gathered their images by placing subjects in an MRI scanner and having them perform two self-control tasks. The first task 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 says 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.
Hedgcock's paper, "Reducing self-control depletion effects through enhanced sensitivity to implementation: Evidence from fMRI and behavioral studies," was co-authored by Kathleen Vohs and Akshay Rao of the University of Minnesota. It will be published in January 2013 in the Journal of Consumer Psychology