When logical conclusions go against beliefs: an ERP study

Abstract

<p>Reasoning is a fundamental human ability, vulnerable to error. According to behavioural measures, we are biased to consider valid the conclusion of an argument based on the veracity of the conclusion itself rather than on the formal logic of the argument. Nowadays, brain imaging techniques can be used to explore peoplés responses as they reason with linguistic materials. Using the Event-Related Potential technique in a categorical syllogism reading task, an N400 enhancement was found for the processing of invalid conclusions preceded by true premises (e.g. <i>All men are mortal</i>). By contrast, when initial premises consisted of socially prejudiced statements previously rated as false (e.g. <i>All blond girls are dumb</i>), valid rather than invalid conclusions enhanced the N400 response. Considering what the modulation of N400 indexes (i.e. word anticipation processes), our data suggests that people cannot follow the logic of an argument to anticipate upcoming words if they clash with veracity.</p