The neural sources of preference instability : a neuroeconomics investigation.

Summary Standard economic theory postulates that individual preferences are stable. However, numerous results from psychology and experimental economics show that human behavior regularly contradicts this fundamental principle. Some factors known to influence value, such as affective context, are not taken into account in economics. Their effects are still considered contingent phenomena - anomalies at the margins of rationality, which as such do not inform theory. Now that brain imaging allows us to formulate and test new hypotheses, we question the contingent character of the influence of context on preferences, with the idea that these "biases" would result from properties inherent to the physical structure that generates behavior, namely the brain. Because they reflect the a priori conditions of any value judgment, they are not contingent but necessary, which explains their prevalence. Our first study proves this hypothesis in the case of context biases: we show that the inertia of brain activity combined with the automaticity of evaluation explains the effects of context on value in monkeys and humans. Our second study shows that trust is encoded in the same brain region as value, suggesting that the can be understood as a second-order value judgment. Finally, our third study shows a behavioral attribution bias leading to interference between value and trust, which was predicted by the combination of results from the first and second studies.