Emotional valence modulates the early (P2/N200) and late (N400/LPC) components in category-based inductive reasoning

Emotions primarily affect the late stages of deductive reasoning, but their impact on inductive reasoning and the role of task-relevance remains unclear. We combined category-based induction task with ERP to examine whether incidental emotional state and task property interact when inferring on genes or diseases. We used neutral, positive, and negative pictures to induce incidental emotional states in participants before they judge the plausibility of the conclusion based on taxonomic (e.g., mouse-mole) and thematic relations (e.g., lizard-mosquito). Behavioral results revealed longer reaction times (RTs) for neutral relative to negative and positive priming under gene task, but not under disease task. The ERP results demonstrated that both positive and negative priming elicited smaller P2 and greater N200 amplitudes compared to neutral priming, which respectively reflected the early enhanced attention and conflict detection processing to emotional stimuli. However, only positive priming significantly enhanced the N400 amplitude, reflecting the generalization of semantic relations. More importantly, negative priming elicited smaller LPC compared to neutral priming under disease task, but not under gene task. This suggests that negative priming involves more relational extraction processing, which is modulated by task relevance. Unlike previous studies that found higher plausible responses to thematic relation in disease tasks, we found higher plausible responses or short RTs, smaller N400 and larger LPC components for taxonomic relative to thematic relation in both gene and disease tasks. These results showed that emotional valence affects both early and middle/late stages of inductive reasoning, advancing our understanding of attention resource attraction and conflict detection mechanism in emotion-influenced reasoning.