The age-old dilemma: do you take your sig other's hints, buy that electronic picture frame, and load it with family highlights from holidays past (yawn)? Or do you go with your gut and get her the unexpected gift of a new XBox-360?

First to the hallowed halls of marketing psychology: In 1956, the psychologist Jack Brehm asked housewives to rank how much they wanted certain household items. Then Brehm asked them to choose between items they’d rated equally desirable, perhaps a vacuum cleaner and a dishwasher. Then Brehm asked the housewives to rank all the items again. In this second pass, housewives who'd chosen dishwashers found them even more desirable than they had in the first round. And they found the item they decided against—perhaps the vacuum cleaner—less desirable than before.

This is a classic example of past-rationalization: of course you made the correct choice between the dishwasher and the vacuum cleaner, because look at their (new) difference in desirability! But does forcing a person to make a tough choice between two objects clarify a preference that already exists, or does this choosing create the preference, itself?

Both, it seems.

Researchers in London watched participants' brains as they pondered and then rated the desirability of various vacation destinations. Then researchers forced them to choose between vacations they'd rated equally desirable.

But researchers could've predicted which vacations the participants would choose—they'd charted how brightly each destination lit each participant's caudate nucleus, a region of the brain linked to anticipating rewards—and more often than not, a participant's choice reflected what their caudate nucleus already knew. So forcing a choice between similar vacations brought existing preferences to light.

Then participants got back in the scanner and rated the destinations again. Like the housewives, participants' caudate nuclei lit brighter than the first time for the vacations they picked, and were dimmer than the first time when imagining the desirability of the vacations they decided against. And so a person's choice also creates—or at least solidifies—a preference.

In other words: choosing something makes it more desirable. One point for the picture frame. But there's still hope: your sig other hasn't compared the picture frame to the XBox-360 and so her anticipation has only boosted the frame, without lowering the game console. Yes, the frame takes on increased importance, but the XBox can still blow it out of the water.

The how includes one of the coolest experimental designs I've run across:

It starts with an interesting treatment for Parkinson’s disease in which a small, battery powered device called a neurostimulator is implanted deep within the midbrain to control symptoms such as tremors and rigidity.

And since surgeons were going to be poking around in the midbrain anyway, and since it's possible for patients to be awake during this neurosurgery, researchers at U Penn devised a little secondary study: why not use microelectrodes to measure the firing rates of dopamine-releasing neurons in patients' substantia nigra during a simulated gambling task?

Here's what they found:

Neurons turned on dopamine when subjects won simulated money. And the dopamine release was proportionate to the amount of money they won. No surprise. But when winning was unexpected—bang!—dopamine skyrocketed, with "winnings" in the brain disproportionate to the amount of winnings in the gambling task.

In other words, while meeting our expectations has a slightly reinforcing effect on our emotional memory, learning, and thus future behavior, something unexpected makes us drastically adjust our worldview. In the mathematics of evolution, it's as if an expected result—no matter how large—is just another dot on an existing curve. But even a small, unexpected result forces us to redraw these curves entirely.

The unexpected has disproportionate power. We'll call this the power of the XBox-360. So don't worry, dude—go with your gut. She'll love it. (Please disregard the cruise-liner-sized holes in this argument.)

Here's a question: which of these two thing would you most like to receive this year? To cover your bases, I recommend both buying your choice and hinting to your sig other that he/she should buy your choice. Better safe than sorry, right? To make attaining said gift of your choice easy, I offer this link to my book Brain Candy: Science, Paradoxes, Puzzles, Logic and Illogic to Nourish Your Neurons.