You’re in a store, trying to choose between similar shirts, one blue and one green. You don’t feel strongly about one over the other, but eventually you decide to buy the green one. You leave the store and a market researcher asks you about your purchase and which shirt you prefer. Chances are that you’d say you prefer the green one, the shirt you actually chose. As it turns out, this choice-induced preference isn’t limited to shirts. Whether we’re choosing between presidential candidates or household objects, research shows that we come to place more value on the options we chose and less value on the options we rejected.

One way of explaining this effect is through the idea of cognitive dissonance. Making a selection between two options that we feel pretty much the same about creates a sense of dissonance – after all, how can we choose if we don’t really prefer one option over the other? Re-evaluating the options after we’ve made our choice may be a way of resolving this dissonance.

This phenomenon has been demonstrated in numerous studies, but the studies have only examined preference change shortly after participants make their decision. Existing research doesn’t address whether these changes in preference are actually stable over time.

In a new article published in Psychological Science, a journal of the Association for Psychological Science, researcher Tali Sharot of University College London and her colleagues examine whether choice-induced changes in preference are fleeting or long-lasting.

The researchers asked 39 undergraduate participants to rate the desirability of 80 different vacation destinations, rating how happy they think they would be if they were to vacation at that location. They were then presented with pairs of similar vacation destinations and asked to choose which destination they would prefer. The participants rated the destinations again immediately after making their choices and once more three years later.

To test whether a sense of agency over the decision makes a difference for choice-induced changes in preference, the researchers looked at participants’ preferences when the participants made the choices themselves and when a computer instructed the participants’ choices.

The results suggest that the act of choosing between two similar options can lead to enduring changes in preference. Participants rated vacation destinations as more desirable both immediately after choosing them and again three years later. This change only occurred, however, if they had made the original choice themselves. The researchers observed no change in participants’ preferences when the computer instructed their choices.

Sharot and her colleagues argue that fact that this effect is robust and enduring has implications for a diverse array of fields, including economics, marketing, and even interpersonal relationships. As Sharot points out, for example, repeatedly endorsing a particular political party may entrench this preference for a long period of time.

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This study was supported by a Wellcome Trust Program Grant to Raymond J. Dolan, a Wellcome Trust Career Development Fellowship to Tali Sharot, and a Sir Henry Wellcome Postdoctoral Fellowship to Stephen M. Fleming.