Event-related potential evidence of semantic mismatch in a 'same-different' reaction time task

In a 'same-different' reaction time (RT) task, suit (spades and/or hearts) target stimuli, and irrelevant suits (distractors) or plus signs (indifferent elements) were presented. The 'same' RT was shorter than the 'different' RT. This 'fast same' effect was independent of the RT increase caused by the distractor stimuli. Event-related potentials (ERPs) in trials with distractor elements were more negative in the 350-600 ms latency range than the ERPs of trials with different irrelevant elements.