On a diet? You'll spend more on impulse purchases

People who exercise self control in some way, such as dieting or trying not to look at or think about something, will tend to make more impulse purchases if given the opportunity, explains a study from the March issue of the Journal of Consumer Research.

Kathleen D. Vohs and Ronald J. Faber (University of Minnesota) point out that opportunities for impulse purchasing have increased with the proliferation of ATMs, shopping on the Internet, and shop-at-home television programs. Instead of gauging desire for things, they are the first to measure actual spending patterns after the exertion of self-control, expanding the literature to include the impulse to buy.

For example, the researchers explore the effects of mental self control in an experiment that asked a group of participants to write down all their thoughts for six minutes. Another group was told that they should also write down all their thoughts – with one exception. The participants were told that if they thought of "a white bear" they were NOT to write it down, but instead to place a check mark at the side of their paper.

The participants were then told that they were taking place in an unrelated study and given $10 to spend on items from the college bookstore. They were told that whatever unspent money was theirs to keep.

Even a small regulatory exercise – the attempt to suppress an innocuous thought about a white bear – caused the participants who had exercised mental self-control to spend and buy more. Those who had just tried to control their thoughts spent an average of $4.05. Those who had been free to write whatever they wanted spent an average of $1.21. Participants who had previously been asked to exercise self-control also bought twice as many items on average as members of the unregulated group.

"Overall, the research shows that people need self-regulatory resources to resist impulse buying temptations, and that these resources can be depleted by prior self-control efforts," write the researchers. "As a result, people should avoid shopping on days when they have earlier exercised great self-control or when starting a new self-improvement program, such as a new diet."
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Kathleen D. Vohs and Ronald J. Faber. "Spent Resources: Self-Regulatory Resource Availability Affects Impulse Buying," Journal of Consumer Research: March 2007.