Natural Rationality | decision-making in the economy of nature


A basic mode of behavior: a review of reinforcement learning, from a computational and biological point of view.

The Journal Frontiers of Interdisciplinary Research in the Life Sciences (HFSP Publishing) made its first issue freely available online. The Journal specializes in "innovative interdisciplinary research at the interface between biology and the physical sciences." An excellent paper (complete, clear, exhaustive) by Kenji Doya presents a state-of-the-art review of reinforcement learning, both as a computational theory (the procedures) and a biological mechanism (neural activity). Exactly what the title announces: Reinforcement learning: Computational theory and biological mechanisms. The paper covers research in neuroscience, AI, computer science, robotics, neuroeconomics, psychology. See this nice schema of reinforcement learning in the brain:

(From the paper:) A schematic model of implementation of reinforcement learning in the cortico-basal ganglia circuit (Doya, 1999, 2000). Based on the state representation in the cortex, the striatum learns state and action value functions. The state value coding striatal neurons project to dopamine neurons, which sends the TD signal back to the striatum. The outputs of action value coding striatal neurons channel through the pallidum and the thalamus, where stochastic action selection may be realized

This stuff is exactly what a theory of natural rationality (and economics tout court): plausible, tractable, and real computational mechanism grounded in neurobiology. As Selten once said, speaking of reinforcement learning:

a theory of bounded rationality cannot avoid this basic mode of behavior (Selten, 2001, p. 16)