Prospective effort and choice

We constantly face the challenge of selecting among actions in pursuit of our goals. Behavioral theories suggest the ubiquity of these choices necessitate a valuation process that integrates expected costs and outcomes. Increased sensitivity to costs in value-based choices, such as reduced willingness to tolerate risk, wait or work for rewards, features prominently in the symptomatology of mental illness. Contrary to classical theories of choice that do not distinguish among cost type, the recent unification of experimental economics, psychology and neuroscience describes the influence of specific costs upon behavioral and neural correlates of subjective value. Despite substantial progress in the understanding of the basis of subjective valuation under delay and risk, the specific influence of effort, the energetic cost of an action, remains largely unknown. Limited existing accounts hypothesize that cost sensitivity during subjective valuation results from separable neural systems related to risk, delay and effort. This dissertation evaluates evidence for distinct neural representation of effort and presents a set of experiments designed to refine normative accounts of effort-based choice. First, I review the neural basis of economic choice under risk and delay. Second, I review limited accounts economic choice under effort. I describe a novel prospective effort task designed and validated to examine effort-based valuation and address potential confounds present in previous studies. In the first experiment, I report novel evidence for discounting of neural activity related to value by prospective effort and conjoint sensitivity to effort costs and expected outcomes in brain regions related to selection and generation of actions. In a second experiment, I examined the influence of prospective effort costs upon delay discounting preferences. This experiment did not find modulation of individual preferences by prospective effort costs. Finally, I discuss our results in the context of existing accounts and potential extensions of the prospective effort paradigm. Overall, I show that prospective effort imposes a specific cost, reflected in behavioral and neural correlates of value, and presents a novel approach to further the understanding of motivated behavior.