Posted 02 May 2020

Willpower: Why self-control is the secret to success by Roy F. Baumeister and John Tierney

Willpower doesn’t know whether it wants to be popular science or self-help; it mostly describes psychology experiments and sporadically proffers advice on increasing your own willpower.

Unfortunately, the advice doesn’t always follow from the science as reported. The authors report on experiments showing that willpower is depleted by doing a task involving the exercise of self-control; subjects perform less well on a follow-up task that also involves the exercise of self-control. They also report on experiments showing that performance is not diminished if subjects are refuelled in between tasks by giving them glucose in the form of sugary food or drink. But then they say that sugar is for the lab, not your diet, and you should eat foods containing complex carbohydrates or low-glycemic fats, which are slowly converted into glucose. They say that psychologists use sugar in experiments for convenience, so that they can observe the effects of glucose quickly and not have to wait for the body to digest more complex foods. But there is no report of any experiment in which subjects do a task requiring self-control, then eat slow-burning foods (or no food, for a control group), then wait a few hours for digestion, then do another task requiring self-control. They should do such experiments, even if it takes more time. As it stands, they are saying we know that lemonade works so you should eat vegetables and nuts. Although it’s known that vegetables and nuts are preferable to lemonade for various health reasons, no evidence is presented here for the effect of such dietary intervention specifically on willpower.

Strangely, the idea that glucose affects performance on lab tasks is presented as an unexpected finding, and transforming the basis of psychology from computer modeling to biology is stated as being a late twentieth century development. Yet the glucose connection was known to Aldous Huxley when he wrote The Doors of Perception in 1954:

“Some of these enzymes regulate the supply of glucose to the brain cells. Mescalin inhibits the supply of these enzymes and thus lowers the amount of glucose available to an organ that is in constant need of sugar. When mescalin reduces the brain’s normal supply of sugar, what happens? Too few cases have been observed, and therefore a comprehensive answer cannot yet be given. But… the will suffers a profound change for the worse.”

Huxley wouldn’t have been guessing about the role of glucose in human biology because his scientific contemporaries did know about this. Nobel Prizes were awarded in the early twentieth century for discoveries about glucose metabolism, and this subject has been covered in physiology textbooks for many years. So there’s no excuse for not controlling for glucose intake in psychology experiments until the late twentieth century (except for academic silos).

Talking of substance control, my (glucose-nourished) mind has come up with another question: when academic psychologists use students on campus as research subjects, do they control for drug usage?

It’s unfortunate that the chapter about dieting for weight loss cites studies by Brian Wansink because many of his studies were retracted in 2017 (after the 2011 publication of Willpower). Some of the advice in that chapter may nonetheless be right, even if not scientifically proven.

Nonetheless, this book does have some interesting examples of the effects of willpower depletion. Just two: (1) A parole board is more likely to release prisoners who appear in court immediately after the judges have had breakfast, lunch, or a snack. (2) Car buyers’ decisions are affected by the order in which the choices of options (style of gearshift knob, interior color, etc.) are presented, meaning that sellers can take advantage of decision fatigue.

On balance, the interesting bits are outweighed by the fact that the popular science bits are long-winded and the self-help bits aren’t helpful.

Finally, the most salient thing about this book for me in terms of actual outcome was the cover. I know that you shouldn’t judge a book by its cover — and I’m not doing so, having already made my judgement on other grounds. However, I must say I think the cover image is inappropriate because it actually negates the message. A photo of a child looking at a plate of marshmallows on a book about self-control? Seriously? Presumably it’s there because the book contains a discussion of the famous experiment by Walter Mischel in which 4-year-olds were left alone in a room with one marshmallow (not a whole plate) and told they could eat it at any time but would get an extra one if they waited for fifteen minutes. A week after I had read that section, I found myself buying a packet of marshmallows in the supermarket. Yes, found myself doing so. Marshmallows were not on my shopping list. My route around the supermarket does not usually take me down the aisle where they are displayed. I had not bought any for several years. But I’d seen the cover image every day for a week. So if you’re going to read this book, either re-cover it or get it as an eBook.

See also my discussion of this book’s take on Parkinson’s Law within my multi-book look at this topic.