Event-related brain responses to emotional words, pictures, and faces - a cross-domain comparison

Abstract

Emotion effects in event-related brain potentials (ERPs) have previously been reported for a range of visual stimuli, including emotional words, pictures, and facial expressions. Still, little is known about the actual comparability of emotion effects across these stimulus classes. The present study aimed to fill this gap by investigating emotion effects in response to words, pictures, and facial expressions using a blocked within-subject design. Furthermore, ratings of stimulus arousal and valence were collected from an independent sample of participants. Modulations of early posterior negativity (EPN) and late positive complex (LPC) were visible for all stimulus domains, but showed clear differences, particularly in valence processing. While emotion effects were limited to positive stimuli for words, they were predominant for negative stimuli in pictures and facial expressions. These findings corroborate the notion of a positivity offset for words and a negativity bias for pictures and facial expressions, which was assumed to be caused by generally lower arousal levels of written language. Interestingly, however, these assumed differences were not confirmed by arousal ratings. Instead, words were rated as overall more positive than pictures and facial expressions. Taken together, the present results point toward systematic differences in the processing of written words and pictorial stimuli of emotional content, not only in terms of a valence bias evident in ERPs, but also concerning their emotional evaluation captured by ratings of stimulus valence and arousal.

Keywords: domain specificity; emotion; event-related brain potentials (ERPs); facial expressions of emotions; language; negativity bias; pictures; positivity bias.

FIGURE 1

Global field power (GFP) waveforms for words, pictures, and faces, averaged over emotion categories.

FIGURE 2

Grand mean waveforms for positive, neutral, and negative words, pictures, and faces at selected electrode locations. Highlighted areas show time windows of analyses for EPN and LPC in the respective stimulus domain. Scalp distributions of significant emotion effects are depicted as differences between indicated emotion categories; time windows correspond to the highlighted areas on the left side. The voltage scale of -1 to 1 μV applies to all topographies but the LPC for pictures, where the corresponding scale is depicted underneath the scalp distributions.

FIGURE 3

Results of post-experimental ratings of stimulus arousal (A) and valence (B). Error bars indicate standard deviations.