Everyone’s inner resolve is occasionally stretched to the limit. Roy Baumeister, a social psychologist at Florida State University believes that self-control requires inner strength and effort and this means you can use it up.
He and Mark Muraven, now at the University of New York, demonstrated this in 1998 by putting volunteers in the position of resisting certain temptations of varying difficulty. After about 5 minutes the volunteers were given a test consisting of a series of impossible puzzles and were monitored to see how long they would persist in trying to solve these. People who had had to resist stronger temptations had less sticking power at the puzzles.
Baumeister believes that this is because we use up our store of willpower resources every time we make the effort to hold back or do something we don’t want to do. Exercising willpower is like exercising a muscle and it takes time for the resources use to be replenished. Making difficult decisions and coping with stress may deplete the same resources, also sapping willpower.
He has since suggested that blood glucose levels are the key to keeping our willpower strong. By giving people a sugary lemonade drink before they completed a willpower exercise, he found that subsequent self-control was not depleted in the same way as in those who had no drink at all or who had an artificially sweetened drink (Psychological Science Vol 19 Page 255). ‘Conscious, effortful control uses energy’ he concludes. This could explain why all-encompassing health drives so often fail. Kicking a habit may take up all your available willpower, leaving very little in the tank to fuel a new exercise regime or healthy eating plan.