FN400 and sustained negativity reveal a premise monotonicity effect during semantic category-based induction

The premise monotonicity effect during category-based induction is a robust effect that occurs when generalization of a novel property shared by many cases is more likely than one shared by few cases. The timing of brain activity during this effect is unclear. Therefore, the event-related potentials (ERPs) underpinning this effect were measured by manipulating the premise sample size (single [S] vs. two [T]) in a semantic category-based induction task, with the conclusion categories either including the premise categories (congruent induction) or not (incongruent induction). The behavioral results replicated the premise monotonicity effect, and revealed that S arguments produced longer reaction times and more conservative response criteria than did T arguments. This suggests that the premise monotonicity effect was affected by both evidence accumulation speed and decision threshold. ERP results demonstrated that the premise monotonicity effect was reflected by two parameters during inductive decision: (1) S arguments elicited larger FN400 amplitudes than did T arguments under congruent induction, which was linked to reduced global similarity, decreased cognitive relevance, and attenuated conceptual fluency and (2) S arguments elicited larger sustained negativity (SN) in the 450-1050-ms time window than did T arguments, which is related to more inference-driven integration and interpretive processes. Our findings provide insight into the complex temporal course of the premise monotonicity effect during semantic category-based induction.