The utilitarian brain: Moving beyond the Free Energy Principle

Abstract

The Free Energy Principle (FEP) is a normative computational framework for iterative reduction of prediction error and uncertainty through perception–intervention cycles that has been presented as a potential unifying theory of all brain functions (Friston, 2006). Decision-making is an important cognitive faculty whose mechanisms must be explained by any theory hoping to unify the brain sciences. This challenge has been accepted by several proponents of the FEP (Friston, 2010; Gershman, 2019). We evaluate these attempts to reduce decision-making to the FEP, using Lucas' (2005) meta-theory of the brain's contextual constraints as a guidepost. We find variants of the FEP unable to explain behavior in certain types of diagnostic, predictive, and multi-armed bandit decision tasks. We trace the shortcomings to the theory's lack of an adequate notion of utility, a concept central to decision-making and grounded in the brain's biological reality. We argue that any attempts to fully reduce utility to the FEP would require unrealistic assumptions, making the principle an unlikely candidate for unifying brain science. We suggest that researchers instead attempt to identify contexts in which either informational or reward constraints predominate, delimiting the FEP's area of applicability. To encourage this type of research, we propose a two-factor formal framework that can subsume any FEP model and allows experimenters to estimate the contributions of informational versus reward constraints to behavior.