Why do behavioral economists consider it helpful to base a theory of economic behavior on the actual mental processes that people use to make decisions? Why do neoclassical economists not care about whether a theory incorporates those actual mental processes?

Neoclassical economics relies on the assumption that individuals are rational decision makers, which is a good starting point when there is no strong evidence suggesting otherwise. Behavior economists, however, show through numerous experiments that individuals are subject to systematic errors when they process information and make decisions. Many of these errors are cognitive and psychological in nature, such as overconfidence, representativeness, and mental accounting, and therefore could (and are shown to) apply to many different individuals. Therefore, it is important to account for these behavior anomalies when we study decision making of the general population. Neoclassical economics do acknowledge the existence of these physiological biases, but argue that as long as such biases average out across a large number of individuals (for example, half of the population make mistakes one way, the other half make the opposite mistakes), then on the aggregate the effect of such biases is negligible.