Kelly McGonigal mentioned recently on her Science of Willpower blog and her Twitter feed this interesting study about consumption of glucose in the brain. In case I started losing you at “consumption of glucose,” let me promise you that there is a great tussel forming up here! Here’s how it goes, although I’m oversimplifying it in order to be able to summarize the whole thing.
Some reputable researchers, including highly-regarded willpower researcher Dr. Roy Baumeister: Willpower is like a muscle. You use up energy when you use willpower, so you tend to get tired out and have less willpower for later. A little bit of sugar can help sometimes help keep willpower perky, though.
The New York Times blog: Willpower is like a muscle, say famous scientists. A little bit of sugar will give you a willpower boost, but don’t tire out your willpower.
Me: Hey, the New York Times and some reputable scientists are saying that willpower uses up energy in the brain and can get used up.
Me, later: Having done a lot more research and thinking, I’m not so sure about the “like a muscle” argument. An alternative hypothesis: maybe people just get annoyed at being asked to do things and get fed up. (Dr. McGonigal added via Twitter, ”What gets exhausted is not the physical willpower energy but what I call ‘willingness.’”)
Dr. Robert Kurzban, a psychologist at the University of Pennsylvania (not responding to my post, but to the original studies): Actually, it doesn’t look as though the brain really does use much extra glucose when we’re exerting a lot of self-control. “That is, if one were to use this aggressive estimate … the brains of subjects categorized as ‘depleted’ in this literature, have, relative to controls, used an additional amount of glucose equal to about 10% of a single Tic-Tac.” (Less than 1/5 of one calorie.)
There’s more to the discussion. For instance, more stressful mental situations can increase heart rate, which can lead to the rest of the body consuming more glucose. And I know that if I spend a long time working hard at mental tasks, I feel worn out afterward in the same way I do after exercise–although all that might well be from that heart rate effect, or some other effect. Based on Kurzban’s information, it’s very unlikely that I get tired out because my brain is using a lot of extra glucose.
Even if we don’t count the useful lesson that science is a series of attempts to explain things people have observed and that those attempts aren’t always right, this whole debate can be useful to us. For instance, we might observe that even if the glucose argument doesn’t hold, there are still ways in which self-control can be “used up.” For instance, in order to exert self-control that goes against our habits, we have to have attention and effort to spare, and those are limited resources. We also probably need some kind of willingness to tackle the challenge, and in some cases that might be something that we can’t use over and over without consequences.
However, there are other factors that make it easier to exert self-control again after exerting it once. One is a sense of accomplishment or control, a belief in the self. Another is encouragement from others, if we happen to get it. Another is that exerting self-control helps build a habit of self-control, although admittedly that habit is likely to pay off more in the long-term than the short. Another is that by exerting self-control in one area, we prove to ourselves that self-control is possible. Yet another is that having self-control often leaves us in better physical and mental condition than not having self-control, in that the kinds of things we tend to do when we don’t have self-control (like eating junk food, being inactive, and bottling up emotions) tend to wear us out or reduce our mental clarity, ability to focus, or physical strength for a while.
My conclusion from all this is that we don’t need to worry too much about using up our willpower: it makes more sense to be concerned about learning as many willpower-related skills as possible, practicing those skills, and focusing our attention and effort where it will do the most good.
Graphic by labguest