Cognitive dissonance has entered the vernacular as shorthand for what people experience when they hold two contradictory opinions at once. But, within psychology, it describes a somewhat distinct process, where people are forced to reject an item they actually like. Given this bit of awkwardness, people are prone to dealing with it in a fairly simple manner: they conclude that they never really liked the item that much in the first place. This finding, which implies that behavior can drive belief instead of the other way around, has remained controversial, but researchers are now claiming to have identified the neural activity that drives cognitive dissonance.

The first scientific description of cognitive dissonance dates to 1956 although, as the authors of a new paper on the subject note, it can be said to date back to Aesop's fable of the fox and the grapes (where the fox decides the grapes were probably no good after it determines that it can't reach them). It is typically demonstrated using a rate-choice-rate process, in which subjects are given the chance to rate a number of similar items. Afterwards, they are forced to choose between two items that they rated identically. After this choice, another round of rating will typically show improved scores for whichever item was chosen, and falling scores for the rejected one.

Recently, some researchers challenged this interpretation, arguing that most rating systems can't capture preferences that accurately, and people may not rate things that carefully. Both of these factors obscure a "true preference" that remains unchanged, and is only revealed when the subjects are forced to make a choice. To support this argument, the researchers used a rate-rate-choice process, and showed that ratings shift in the direction of the choice even before it is made.

So, is cognitive dissonance real? In the new work, the authors claim to have figured out ways of demonstrating it exists. For starters, they created a group of subjects that, instead of being given the choice of two items, were forced to watch as a computer decided for them. Then, once that choice was made and a rerating occurred, the subjects were given the option of having their own choice registered. Finally, they claim to have used functional MRI to identify brain activity associated with cognitive dissonance.

As expected, the authors are able to demonstrate cognitive dissonance in action: once an individual has chosen against an item, their ratings of it plunge. This effect was much, much smaller when a computer made a choice for an individual, although the later personal choice offered these subjects restored a bit of its impact. So, the researchers have confirmed both the previous work on cognitive dissonance and that of its critics: some fraction of the effect seems to be driven by people actually having stronger preferences than they state, but not all of it.

How does this play out in the brain? The authors focused on the striatum, which has been associated with rewards processing. In all but the cognitive dissonance condition, activity in the striatum increased when the subject was deciding on a final rating. When subjects are rating the choice they rejected, however, activity in this brain region plunged. They also saw increased activity in the anterior cingulate cortex that correlated with how strongly a subject exprienced cognitive dissonance. These results convince them that they've nailed down a neural basis for the phenomenon, and thus that it must exist.

There's a small problem here. One is that the research only focused on areas of the brain already thought to be involved in decision-making processes. If there's a strong signal in another area of the brain, it's not clear that the authors would have detected it. And, in fact, they did discover other areas of activity. "While here were other regions correlated with subjects' self-reported preferences," they state in the discussion before noting, "the striatum was the only region showing the predicted pattern of preference change." In other words, there were different regions of the brain that showed patters that undercut the argument for cognitive dissonance.

The paper dismisses these, saying that this activity might reflect some unrelated process, like the degree of excitement a choice offers. But there's something a bit unsatisfying about the fact that a similar analysis wasn't performed for all regions of the brain that displayed differential activity.

Even with that weakness, however, the study pretty clearly shows that behavior isn't driven simply by what we believe; our actions can feed back and alter our beliefs. Which, really, shouldn't have surprised anyone, given the degree of post-hoc rationalization that most people engage in. However, as the authors note, this fact seemed to have escaped those who developed the economic systems that assume that people are rational actors.

PNAS, 2010. DOI: 10.1073/pnas.1011879108 (About DOIs).