NPR: Your Self-Control Can Be Depleted

What Your Brain Looks Like When You Lose Self-Control

June 22, 2012

[The following is a conversation with a researcher who has proved what I’ve always known to be true–there is a limit to my willpower.] 

Ever wonder why you worked so hard to avoid the lasagna at dinner only to give in to your craving for not one but two helpings of cake for dessert? Well, new research may hold some answers to this vexing question. A new study in the Journal of Consumer Psychology confirms what we’ve been – what we’ve known for some time, and that is each of us has an internal reservoir of self-control. We have a reservoir of self-control that it depletes. Every time we resist a temptation, we use a little bit of it up.

But for the first time, researchers have taken pictures of the brain to show what was happening when a person exerts and then loses self-control. Dr. William Hedgcock was a co-author of the study. He is a neuroscientist and assistant professor of marketing at the University of Iowa. He joins us from Denver. Welcome to SCIENCE FRIDAY.

DR. WILLIAM HEDGCOCK: Oh, thanks for having me.

FLATOW: Well, first, let me back up a bit because I think it would be surprising to most people to learn that we actually have a reservoir of self-control.

HEDGCOCK: Sure. So this is a theory called regulatory resource depletion. And like you said, when people exert self-control, what we see is people have a hard time exerting self-control later, so this idea of one resource may be, you know, not intuitive. But I think most of us have had this sort of experience where you exert self-control at one point and then end up succumbing to temptation later.

FLATOW: Mm-hmm. And where is that center of self-control?

HEDGCOCK: Well, what we’re finding is that the center seems to be the dorsolateral prefrontal cortex, so it’s an area that’s sort of near the temple and underneath the temple of your head.

FLATOW: Hmm. And how do we know that that’s where it is?

HEDGCOCK: Well, so we ran an fMRI study where we had subjects come into the scanner. They first exerted self-control, and we saw them having activation in areas like the dorsolateral prefrontal cortex and the anterior cingulate cortex. And this is what, you know, we would have expected. Then we had them exert self-control later on a subsequent task, and we saw less activity in this dorsolateral prefrontal cortex area.

FLATOW: So it had been depleted in – some of their self control was gone.

HEDGCOCK: Yeah. So we saw behaviorally that they had less self-control, and that seemed to be correlated with the fact they had less activity in that area.

FLATOW: Now, is the reservoir a reservoir of chemicals? Is it a reservoir of neurons? What exactly is the reservoir?

HEDGCOCK: So we don’t really know that yet. We do know that there’s less activity in that area. It seems unlikely that it’s a neurotransmitter, for instance, but we would need some follow-up studies to find out exactly why is it less active there.

FLATOW: Mm-hmm. And what kind of test do you do when you test people for their self-control? Do you put pie in front of them and say, you can only have one bite or what?

HEDGCOCK: Well, that certainly – some people do that. So we’ll put people in front of brownies or something and then see later, would they like to choose brownies versus a healthy snack or – also, we test them on things like, will they perform well on a cognitive task. But in the scanner, we couldn’t do that. It’s difficult to, you know, put a pie next to a person in the scanner.


HEDGCOCK: So what we did was something a little bit more sterile than that. We had them look at a fixation point on a screen, and we flash words underneath the fixation. And the words would move around and – but they’re very close to the fixation. We told subjects to ignore them and definitely not read them, but this was difficult or, for the most part, impossible for subjects to do. So it required self-control on their part to not read the words.

FLATOW: Don’t think of pink elephants.

HEDGCOCK: Yeah. Well, so that’s another version of – or another way to manipulate self-control. You could have them not think about elephants, which is difficult to do once we mention it to you.

FLATOW: Right. 1-800-989-8255. Talking with Dr. William Hedgcock about exerting self-control. And so can you actually tell at the moment by looking at the scan when, uh-oh, they’ve lost their self-control?

HEDGCOCK: Well, what we saw was sort of a gradual depletion over time. We didn’t see a particular timeframe. And by the way, our subjects sometimes were able to exert self-control later. It’s not like they completely lost it. They were just less able. They just occasionally would succumb to temptation more frequently than when they were not depleted.


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