Why We Buy: Weighing Pleasure Vs. Pain

Jan. 5, 2007 -- Attention, shoppers: A battle between pleasure and pain may be going on in your brain.

When people are deciding whether to buy something, their brain apparently weighs the pleasure of making the purchase against the pain of spending the money.

That's according to research published in the January issue of Neuron.

The researchers included psychologist Brian Knutson, PhD, of Stanford University; economist George Loewenstein, PhD, of Carnegie Mellon University; and Drazen Prelec, PhD, of the Massachusetts Institute of Technology's Sloan School of Management.

Their findings defy an economic theory that purchasing decisions are a trade-off between current pleasure (buying something now) and future pleasure (buying something else later), Loewenstein tells WebMD.

"We suspected that that's not the way the brain solves the problem of how much to spend," Loewenstein says.

Spend Now or Later

"Suppose you're trying to decide should you go out to a nice dinner tonight," Loewenstein explains. "Do you really know what it is you're going to be giving up in the future? No. You don't have a clue."

"And suppose you did know what it was going to be," Loewenstein continues.

"Suppose it was going to be some tiny fraction of your child's education or something like that 20 years from now. That just wouldn't be very motivating."

So he and his colleagues tested another theory: that purchasing is a mental tug-of-war between pleasure and pain.

Speed Shopping

In the experiment, the researchers gave 26 healthy young adults $20 to spend.

But instead of shopping online or at a mall, participants made their purchases in a lab while having their brains scanned with functional magnetic resonance imaging (fMRI).

During the brain scans, The researchers showed participants a picture of an item such as gourmet chocolates, books, DVDs, clothes, clocks, and cameras.

Within a second or two, the item's price -- scaled to fit the participants' $20 budget -- appeared below the picture.

The participants quickly clicked "yes" or "no" buttons to buy the item or not, spending a total of four seconds each on 80 items displayed one by one.

Each participant bought, on average, 23 of the 80 items in the experiment, giving their opinions on the products and prices right after they finished the test.