Influence of typicality in category-based fear generalization: Diverging evidence from the P2 and N400 effect

The conceptual properties of a conditional stimulus could contribute to human fear generalization, but how typicality influences fear generalization involving different conceptual hierarchies remains unclear. This study used event-related potential technology to investigate this in four categories of generalized stimulus (GS). We divided the GS into four categories: inferior typical members of conditioned stimulus (CS+) (TCS+), inferior atypical members of CS+ (ATCS+), inferior typical members of CS- (TCS-), and inferior atypical members of CS- (ATCS-). The CS+ groups elicited a larger P2 versus the CS- groups suggesting that aversive stimuli can automatically capture attention with timely avoidance of danger. Stimulus type (CS+; CS-) and typicality (typical; atypical) showed an interaction with N400. The elicited N400 was larger for atypical than typical members in CS- groups, but not in CS+ groups. Fear emotion elicited by CS+ may feature restrained semantic networks, dissipating typicality effects. Separate processing stages may modulate category-based fear generalization, with P2 representing first-stage low-level perceptual processing, and N400 second-stage high-level cognitive processing.