Neural correlates of the belief-bias effect in syllogistic reasoning: an event-related potential study.

This study investigated electrophysiological correlates of belief-bias effects in syllogistic reasoning. Event-related brain potentials were recorded for minor premises with which participants were required to draw a logic conclusion during three conditions: the inhibitory belief condition (IBC, the belief is inhibitory to the logical task), the facilitatory belief condition (FBC, the belief is facilitatory to the logical task), and the baseline condition. The results demonstrated a more positive event-related potential deflection during IBC and FBC conditions than during the noninference baseline condition in both the 300-500 and the 1000-1600 ms time windows. Moreover, IBC elicited a more positive event-related potential deflection (P500) than did FBC across central-frontal cortical regions during the 300-600 ms interval. Therefore, this study observed a clear belief-bias effect, and the enhanced P500 activity during IBC, which relates to the belief bias that obstructs normal inferences, most likely reflects an inhibition to beliefs during later relation integration stage.