Neural substrates underlying the expectation of rewards resulting from effortful exertion.

Why do people persist-or stop-when rewards require effort? Such choices are often framed as a trade-off between reward and cost, yet this conceptualization overlooks a fundamental determinant: expectations. Economic theories propose that labor supply is reference-dependent, responding to deviations from expected earnings, but whether such reference points govern effort and how they are implemented in the brain has remained unknown. Using an incentivized grip-force paradigm with functional magnetic resonance imaging, we experimentally imposed reward expectations independent of outcomes. Effort provision shifted systematically with these expectations, demonstrating that individuals evaluate exertion relative to a reference point rather than absolute incentives. Activity in the ventral striatum encoded both prospective reward expectations and deviations between realized and expected earnings, and these signals predicted inter-individual differences in reference-dependent effort. These findings identify a neural mechanism by which expectations recalibrate the value of exertion, revealing reference dependence as a fundamental principle of motivated behavior.