17 October 2007

Self-control wearies brain

If you have a hard time suppressing all your unhealthy habits, new research suggests you can blame it on your brain.

If you have a hard time suppressing all your unhealthy habits, new research suggests you can blame it on your brain.

Giving into temptation -- whether to cheesecake, cigarettes or drugs -- is a common human failing, and now the new findings tie this weakness to a limit in the brain's capacity for resisting temptation. Too much self-control, the researchers say, may weary the brain.

The study, published in the journal Psychological Science, included 40 college students who had their brain activity recorded as their capacity for self-control was tested.

How the study was conducted
First, the students watched a distressing movie. Half were told to try to suppress their emotions while watching the film and show no outward signs of their feelings. The rest were simply told to watch the film carefully.

Immediately afterward, all of the study participants took a test known as the Stroop task. This test requires the taker to look at the words "red" and "green," written in either a red or green font. They then have to identify the word's colour, and not the word itself. Doing so requires a form of self-control.

The students were outfitted with electrodes that recorded their brain wave activity as they performed the test.

In general, the study found, students who'd been asked to control their emotions during the movie performed more poorly on the colour-naming task. Moreover, they showed evidence of weaker activity in an area of the brain called the anterior cingulate cortex (ACC).

Self-control in brain
"I think these findings ground self-control in the brain," lead study author Dr Michael Inzlicht told Reuters Health.

"It suggests that the anterior cingulate cortex -- a part of the brain that plays a watchtower role, monitoring for goal violations -- has its limits," explained Inzlicht, of the University of Toronto Scarborough in Canada.

The ACC, according to Inzlicht, can become "overwhelmed" by too many self-control tasks and lose some of its effectiveness. In any one person, this may manifest as an increase in mistakes, or a lack of motivation to tackle a difficult job, for example.

Limited resources
Inzlicht explained that in general, when people try to exercise restraint in one area -- sticking with a diet, for example -- self-control will likely wane in another area. For the dieter, this could mean difficulty with refusing cigarettes, concentrating on work or keeping emotions in check.

Of course, Inzlicht pointed out, we all vary in our natural capacity for self-control. Exercising restraint in many areas of life may be easy for one person, and impossible for another.

More research is needed to understand why people vary in their self-control capacity, and whether this baseline capacity can be increased, Inzlicht said.

SOURCE: Psychological Science, November 2007. – (Reuters Health)

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Mind Centre

October 2007


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