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Declining house prices, rising job layoffs, skyrocketing oil costs and a major credit crunch have brought consumer confidence to its lowest point in five years. With a relatively long recession looking increasingly likely, many American families may be planning to tighten their belts.

Interestingly, restraining our consumer spending, in the short term, may cause us to actually loosen the belts around our waists. What's the connection? The brain has a limited capacity for self-regulation, so exerting willpower in one area often leads to backsliding in others. The good news, however, is that practice increases willpower capacity, so that in the long run, buying less now may improve our ability to achieve future goals — like losing those 10 pounds we gained when we weren't out shopping.

The brain's store of willpower is depleted when people control their thoughts, feelings or impulses, or when they modify their behaviors in pursuit of goals. Psychologist Roy Baumeister and others have found that people who successfully accomplish one task requiring self-control are less persistent on a second, seemingly unrelated task.

In one pioneering study, some people were asked to eat radishes while others received freshly baked chocolate chip cookies before trying to solve an im possible puzzle. The radish-eaters abandoned the puzzle in eight minutes on average, working less than half as long as people who got cookies or those who were excused from eating radishes. Similarly, people who were asked to circle every "e" on a page of text then showed less persistence in watching a video of an unchanging table and wall.

Other activities that deplete willpower include resisting food or drink, suppressing emotional responses, restraining aggressive or sexual impulses, taking exams and trying to impress someone. Task persistence is also reduced when people are stressed or tired from exertion or lack of sleep.

What limits willpower? Some have suggested that it is blood sugar, which brain cells use as their main energy source and cannot do without for even a few minutes. Most cognitive functions are unaffected by minor blood sugar fluctuations over the course of a day, but planning and self-control are sensitive to such small changes. Exerting self-control lowers blood sugar, which reduces the capacity for further self-control. People who drink a glass of lemonade between completing one task requiring self-control and beginning a second one perform equally well on both tasks, while people who drink sugarless diet lemonade make more errors on the second task than on the first. Foods that persistently elevate blood sugar, like those containing protein or complex carbohydrates, might enhance willpower for longer periods.

In the short term, you should spend your limited willpower budget wisely. It can be counterproductive to work toward multiple goals at the same time if your willpower cannot cover all the efforts that are required. Concentrating your effort on one or, at most, a few goals at a time increases the odds of success.

Focusing on success is important because willpower can grow in the long term. Like a muscle, willpower seems to become stronger with use. The idea of exercising willpower is seen in military boot camp, where recruits are trained to overcome one challenge after another.

No one knows why willpower can grow with practice, but consistently doing any activity that requires self-control seems to increase willpower 一 and the ability to resist impulses and delay gratification is highly associated with success in life.