Past Events

Rewards induce learning (positive reinforcement), approach behavior, economic decisions and positive emotions (pleasure, desire). We investigate basic neuronal reward signals during learning and decision-making, using behavioral and neurophysiological methods. Certainty equivalents from behavioral choices suggest that monkeys are risk-seeking with small rewards and risk neutral and then risk avoiders with larger rewards (juice volumes of 0.05-1.2 ml). The animals’ choices are meaningful in satisfying first, second and third order stochastic dominance. The reward prediction error signal of dopamine neurons codes subjective value as common currency derived from different rewards, temporal discounting and risk. Neuronal satisfaction of first and second order stochastic dominance suggests meaningful processing of value under risk and incorporation of risk into subjective value. Assessment of economic utility goes one step further and determines subjective value as a mathematical function of objective value (of liquid reward). Our monkeys show initially convex and then concave utility functions with increasing rewards, confirming the risk attitudes derived from certainty equivalents in direct choices. The dopamine signal follows closely the nonlinear utility function and thus codes a prediction error in economic utility. These data unite concepts from animal learning theory (prediction error) and economic decision theory (utility) at the level of single reward neurons.

For the last century, economists have assumed that agents have 'deep' time preferences -- in other words, agents value pleasures and pains in t years more than pleasures and pains in t+1 years. By contrast, philosophers have argued that discounting future rewards results from `'myopia,’’ i.e. imperfect foresight. We develop this alternative hypothesis. Specifically, we show that time discounting arises naturally when a perfectly patient Bayesian decision-maker receives noisy signals about the future (instead of being able to make noiseless…

The capacity for cognitive control, one of the defining characteristics of human cognition, is also remarkably limited. Typically, people cannot engage in more than a few — and sometimes only a single — control-demanding task at once. Limited capacity was a defining element in the earliest conceptualizations of cognitive control, it remains one of the most widely accepted axioms of cognitive psychology, and is even the basis for some laws (e.g., against the use of mobile devices while driving). It…