Argument evaluation, Fast and Slow: Deliberation boosts justification strength discrimination in reasoning problems

While recent research shows that reasoning underpins both the production and assessment of arguments, "fast and slow" dual process theories of reasoning devoted little attention to argument evaluation. Specifically, little is known about how people distinguish between strong, explicit justifications and weaker, implicit ones, or how intuitive evaluations differ from slower, deliberate ones. Across three studies, participants solved classic reasoning problems (variants of the bat and ball problem) and rated the strength of arguments supporting different answers to these problems. Ratings were made either under time pressure and cognitive load (intuitive) or without constraints (deliberate). Results showed participants consistently gave higher ratings to stronger, explicit arguments. They also rated arguments that matched their own response generally higher than opposing arguments, under both intuitive and deliberate evaluation. Although participants showed some basic intuitive sensitivity to justification quality, deliberation significantly improved the ability to discriminate justification strength across all argument types. These findings highlight the critical role of both intuition and deliberation in argument evaluation.