How can I resist temptation?

What's happening in the brain when we form habits?
14 January 2014

Interview with 

Molly Crockett, University College London


Ginny -  Our first guest tonight is Molly Crockett from the Wellcome Trust Centre for Neuroimaging at University College London.  Hi there, Molly.

Molly -   Hello.

Ginny -   Now, as part of your work, you investigate willpower and that's something that everyone needs when they're trying to stick to their New Year's resolutions.  It's so difficult to resist that tempting bar of chocolate when you're trying to eat healthily.  Why is it so tricky?

Molly -   Well, it's a classic example of a conflict between our long term goals and our short term goals.  The problem is that when we're trying to resist a temptation that's right in front of us, that short term goal is really smacking us in the face and the long term goal is more distant in our minds.

Ginny -   So, we've got the short term goal of, "Chocolate is tasty.  I really want to eat it" and that's almost overpowering our long term, "No, I'm trying to be healthy.  I should be eating my greens" that sort of thing.

Molly -   Exactly.

Ginny -   What parts of the brain are actually involved of the two different bits that are trying to take over?

Molly -   Well generally, we see willpower in the brain as involving a competition between brain structures that are involved in reward processing including the ventral striatum and the medial prefrontal cortex, and brain structures that are involved in self-control, and sort of inhibitory control that includes the more lateral aspects of prefrontal cortex including the dorsolateral and inferior frontal gyrus.

Ginny -   So, is there anything we can do to make it easier for ourselves if we are trying to stick to a New Year's resolution?  What can we do to prevent this temptation from taking over?

Molly -   Well, we found a number of studies looking at this and willpower is of course the main strategy that we think of when we think about self-control.  But it turns out that there's another strategy that we can use that actually can be more effective than willpower.  So, willpower of course is when we're using our self-control to resist something that's right in front of us.  But there's another strategy called pre-commitment and that's when we take steps now to prevent our future self from being exposed to temptation in the first place.  So, the best example of this is, if you want to avoid eating unhealthy foods, you just don't buy them at the shop in the first place so that they're not even around to tempt you.  We've done some experiments to show that pre-commitment can actually be more effective than willpower when you're trying to reach your goal.

Ginny -   So, how do you do an experiment looking to something like that?

Molly -   Well, our experiments were inspired by the classic studies done several years ago by Walter Mischel.  In those experiments, they looked at how little kids were able to resist eating a marshmallow that was sitting right in front of them.  We wanted to do a study in adults and we focused on young men.  We didn't think that marshmallows would be as tempting for the young men.  So, instead of using marshmallows as temptations, we used enjoyable pictures of women.  These pictures, we had the men rate them before the experiment so we had a large set of pictures.  Some of them were just moderately enjoyable and some were extremely enjoyable for them.  What we did was we gave them a choice.  They could see a sort of okay picture now or they could wait and after a delay, they could see a highly rated picture.  We looked at how they made those kinds of choices in different settings and the willpower condition, they had to basically wait for the large reward, the really enjoyable picture.  But they had the option to choose the small reward - the less enjoyable picture at any time.  However, in the pre-commitment condition, before they were faced with a temptation, we asked them, "Would you like to pre-commit to see the large picture?"  So, they had the option to basically remove that temptation from their choice space.  What we found is that when they had the option to pre-commit, many people did and this made them more likely to receive the picture that they wanted the most than when they had to resist the temptation sitting in front of them.

Ginny -   Was that the case for everyone?  Was it quite standard or did it vary a lot from person to person?

Molly -   Well, it varied a lot from person to person both for willpower and for pre-commitment.  So, we had a lot of variability in our samples.  Some people were really good at resisting temptation and some people were less good at resisting temptation.  That was of course correlated with pre-commitment.  So, we can think of a sort of general self-control skill that can be deployed in either willpower or pre-commitment situations.  But interestingly, when we looked at the benefits that people receive from the opportunity to pre-commit, so how much receiving the large reward improved when you had the opportunity to pre-commit?  Those benefits were actually stronger for the people who were worse at self-control which makes sense.  They had more room for improvement.  But what was interesting was, we also saw differences in the brain when we compared people with high or low willpower.

Ginny -   What kind of differences did you see?

Molly -   What we found was specifically, when we gave people the opportunity to pre-commit to a large reward, those people who had the most trouble with willpower showed stronger activation in their reward networks when we gave them the opportunity to pre-commit.  So, it was almost as though the brain could sort of sense the benefits of pre-commitment when you're making this decision.

Ginny -   So, if you're someone who really struggles with willpower then it's very important to do this pre-commitment thing to make sure you don't buy the unhealthy foods, you don't allow yourself that time to give in to those urges.  Is that what we're getting from this?

Molly -   Exactly and I think the really powerful message here is that self-knowledge can go a long way in helping you achieve your goals.  If you can recognise that you're really bad at willpower, you're not doomed to fail in reaching your goals.  It just means that you have to take some steps to make sure that you don't face with the temptation.


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