Table 1.

Key terms

Expected value In economics, a measure of benefit associated with an option expressed in a theoretical common currency used to compare disparate goods. In animal learning, expected reward associated with an action or stimulus (associative strength). Thought to be represented in the human ventromedial prefrontal cortex (vmPFC).

Reinforcement learning (RL) Statistical account of learning, wherein the discrepancy between the actually received and expected reward (prediction error) is the learning signal, used to update expected value. The goal of RL is to estimate the values of available options from experience and in order to maximize reward.

Value-based choice Selection of actions informed by their values. Choices require greater cognitive effort when action values are close. Choices can be exploitative (favoring options with known high value) or exploratory (sampling lower-value alternatives, typically under uncertainty).