The Effects of Belief and Logic in Syllogistic Reasoning: Evidence from an Eye-Tracking Analysis

Abstract

Studies of syllogistic reasoning report a strong non-logical tendency to endorse more believable conclusions than unbelievable conclusions. This belief bias effect is found to be stronger with invalid arguments than with valid ones. An experiment is reported in which participants’ eye-movements were recorded in order to gain insight into the nature and time course of the reasoning processes associated with experimental manipulations of logical validity and believability. Results are considered in relation to predictions derivable from contemporary accounts of belief bias. The logical status of conclusions was found to influence the duration of gazes, supporting the view that invalid conclusions are more demanding to evaluate than valid ones and the idea that a valid-invalid processing distinction underpins the interaction that is observed between logic and belief. Predictions concerning effects of believability upon gaze behaviour that were derivable from the mental models account (e.g., Oakhill & Johnson-Laird, 1985) gained little support. The paper argues for the value of eye-movement analyses in reasoning research as an important adjunct to existing process-tracing techniques.