The trembling hand unraveled: the motor dynamics and neural sources of choice inconsistency

Ample evidence shows that humans violate fundamental economic axioms. Yet, the neural mechanism underlying inconsistent (or irrational) choices remains obscure. Here, we aim to show that inconsistent choices could rise either due to value miscalculations or due to motor errors during task execution. We report the results from two independent behavioral and neuroimaging studies. Subjects completed a risky-choice task to test their inconsistency levels, followed by two novel tasks, designed to solely examine motor output. We recorded mouse trajectories during task execution and designed 34 features to analyze choice dynamics. We show that choice dynamics predict inconsistency levels, even when motor output was absent any valuation elements. In the neuroimaging study, we show that inconsistency is tied to noisy value computations in reward circuits, but at the same time, is also related to noisy neural motor dynamics. These findings suggest that (at least) two neural sources of noise contribute to inconsistent choice behavior.