The latest laboratory work reveals that self-control has a physical basis and is dramatically affected by simple things like eating and sleeping. A life-changing business decision may go in different directions depending on whether it’s made before or after lunch.
My co-author, professor Roy Baumeister, started out as something of a sceptic. But then he observed willpower in the laboratory: how it gives people the strength to persevere, how they lose self-control as their willpower is depleted, and how this mental energy is fuelled by glucose in the body’s blood stream. He discovered that willpower, like a muscle, becomes fatigued from overuse but can also be strengthened through exercise.
We often think of willpower as an extraordinary force that can be summoned to deal with emergencies. But that’s not what Baumeister has found. Most major problems centre on a failure of self-control: compulsive spending and borrowing; underachievement at school; or procrastination at work; alcohol and drug abuse; unhealthy diet; lack of exercise; chronic anxiety; explosive anger.
But your supply of willpower is limited, and you use the same resource for many different things. Each day may start off with your stock fresh and renewed. But then, all day, things chip and nibble away at it.
The link between willpower and decision making works both ways: Decision making depletes your willpower and, once depleted, you’re less able to make decisions. If your work requires you to make hard decisions all day long, at some point you’re going to be depleted you will start looking for ways to conserve energy. And the most tiring decisions are the ones that seem tough to you, even if they seem obvious to others.
This depletion isn’t intuitively obvious, especially when it comes to appreciating the impact of making decisions. Virtually no one has a gut-level sense of just how tiring it is to decide. Even hypothetical decisions deplete energy. After making some tough decisions, remember that your self-control is going to be weakened.
The problem of decision fatigue affects everything from the careers of chief executives to the prison sentences of criminals appearing before weary judges. It influences the behaviour of everyone, every day. Yet few people are even aware of it. When asked whether making decisions would deplete their willpower and make them vulnerable to temptation, most people say no.
In one study, people were asked to imagine that they had $10,000 (£6,286) that they did not need in a savings account. Then they were presented with an investment opportunity described as average risk and above-average rate of return. When people were not depleted of willpower, most of them said they would make the investment. Depleted people, in contrast, decided to leave the money where it was. Their decision didn’t make any sense financially – but it was easier than making a decision.
Forget the image of starving artists (or City workers) who do great things by working around the clock. Self-control is most effective if you take good basic care of your body. The more that researchers study sleep deprivation, the more nasty effects they keep discovering. A big mug of coffee in the morning is not an adequate substitute for enough sleep.
Beware of making binding decisions when your energy is down – you’ll tend to favour options with short-term gains and delayed costs. A rested will is a stronger will.
John Tierney is a journalist at the New York Times. This is an exclusive extract from Willpower: Why Self-Control is the Secret to Success, which Tierney co-wrote with Roy F. Baumeister, professor of psychology at Florida State University. It is published in paperback today (Penguin, £9.99).