Common and distinct brain responses to detecting top-down and bottom-up conflicts underlying numerical inductive reasoning.

Complex reasoning problems are commonly influenced by a combination of top-down and bottom-up conflicts; however, the common and distinct brain responses to the two types of conflicts have remained unclear. Participants were required to identify the hidden rules in a number series completion task, which included identity condition (e.g., 13, 13, 13), perceptual mismatch condition (bottom-up conflict, e.g., 13 13 +≡), and relational mismatch condition (top-down conflict, e.g., 13 13 14). The ERP results showed that (a) both the perceptual and relational mismatch conditions triggered greater P200, N200, P300, and late positive component than the identity condition, reflecting attention reallocation, perceptual template deviations, feelings of uncertainty, and working memory updating, respectively, and (b) smaller N400 and decreased late negative component were found in the relational mismatch condition in contrast to other conditions, which suggested that changing number values violated rule expectancy as top-down conflict. Therefore, multiple strategies were utilized to detect the conflicts underlying complex reasoning problems.