Nonlinearities in Decision Making: Tempora! Asymmetries in Perceptual Evidence Accumulation

Abstract

Using human behavioural performance and a choice-correlated neural signature as complementary metrics of integration of noisy, changeable evidence about the motion direction of dots, we tested for nonlinearities in the integration of evidence over time. Participants showed a bias for relying more on evidence early in the sample sequence, and a bias for evidence favouring the opposite choice to that previously accrued to have a disproportionate impact on the outcome of the decision. Results challenge the notion that time pressure is the primary determinant of a bias for early evidence. This study also provides a further demonstration of the potential for a lateralized, effector-specific MEG signa! to be used as a tool in arbitrating between theories of the dynamics of decision making.