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This Is Your Brain on Shopping
An fMRI study determines where the brain appraises products and evaluates prices
By Nikhil Swaminathan

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A research team led by Stanford University neuroscientist Brian Knutson has identified the parts of the human brain that respond when presented with a product and those that then act as we decide on whether or not to purchase it. The group reports its findings in this week's issue of Neuron.

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Twenty-six subjects were scanned while they took part in a task called SHOP, short for "Save Holdings Or Purchase." A product, such as a box of Godiva chocolates or a DVD of the popular TV show The Simpsons, would be displayed on a screen in front of them. After four seconds, a price would be shown below the item. Four seconds later, a box would appear on each side of the screen--one labeled "YES," the other labeled "NO"--at which point the participant decided whether to buy or to pass on the product.

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Researchers discovered that when the product first flashed on the screen it activated the nucleus accumbens, a section near the middle of the brain that has been implicated in the brain's reward center, effectively appraising the item. When the price appeared, the scientists noticed activity in the mesial prefrontal cortex, a region of the brain known for higher executive functions. Its activity seemed to vary according to the difference between what someone would pay for an item and its actual cost, as if in error adjustment. Finally, the response of the insula (a lateral section of the brain's cortex known to activate during responses to negative stimuli) depended on the purchasing decision--activity there increased when a participant nixed a purchase. "What we're looking at is not so much the brain's reaction to products and prices as a person's subjective reaction to the products and prices," Knutson says. "Is the product preferable? And is the price too much?"

[NOTE: and below we have the requisite quote from neuroeconomist-for-hire, Colin Camerer]

...the findings of the paper illustrate what behavioral economists label "transaction utility"--"the special pleasure or pain we get from knowing we got a good deal or got ripped off"--because of the response of the insula, the region associated with negative emotions like disgust. "This shows there is an automatic 'is it worth it?' process," he says, "that has a rapid emotional reaction if the answer is 'no.'"