Validating the truth of propositions: behavioral and ERP indicators of truth evaluation processes.

We investigated processes of truth validation during reading. Participants responded to 'true' and 'false' probes after reading simple true or false sentences. Compatible sentence/probe combinations (true/'true', false/'false') facilitated responding compared with incompatible combinations (true/'false', false/'true'), indicating truth validation. Evidence for truth validation was obtained after inducing an evaluative mindset but not after inducing a non-evaluative mindset, using additional intermixed tasks requiring true/false decisions or sentence comparisons, respectively. Event-related potentials revealed an increased late negativity (500-1000 ms after onset of the last word of sentences) for false compared with true sentences. Paralleling behavioral results, this electroencephalographic marker only obtained in the evaluative mindset condition. Further, mere semantic mismatches between subject and object of sentences led to an elevated N400 for both mindset conditions. Taken together, our findings suggest that truth validation is a conditionally automatic process that is dependent on the current task demands and resulting mindset, whereas the processing of word meaning and semantic relations between words proceeds in an unconditionally automatic fashion.