Previous studies showed enhanced memory for emotional stimuli compared to neutral ones: participants remember emotional words, pictures and events better in both recall and recognition tasks. Furthermore there is some evidence for faster processing of emotional stimuli compared to neutral ones. The mechanism(s) underlying these effects are mostly unknown. The aim of the present study was to elicit this speed advantage for emotional stimuli in a simple word comprehension paradigm according to behavioral parameters, and to localize this effect within the information processing system by means of recording event-related brain potential (ERP) components.
A lexical decision task was performed by 18 participants (11 women) while ERPs were recorded from 36 electrode sites. Stimuli were 240 German verbs and 240 pseudowords. Words were emotionally positive (e.g. ENJOY), negative (e.g. ANNOY) or neutral (e.g. PASTE) as determined by independent ratings. Reaction times showed an emotional valence effect especially for the items that had received the most consistent valence ratings. Emotionally negative verbs were always responded to faster than neutral verbs. Positive verbs were also faster than neutral ones but only when RTs were relatively fast. ERPs did not differ as a function of valence before the start of the late positive complex (LPC). Negative verbs elicited a larger parietal positive-going LPC than both neutral and positive verbs between 450 and 550 and again between 650 and 700 ms. Therefore the effects of emotional valence as observed here seem to be localized in late perceptual processes, and probably also later.