Abstract
In fixation-related potential (FRP) experiments stimuli can be presented simultaneously, whereas classical event-related potential (ERP) settings are restricted to a serial presentation. Hutzler et al. (2007; Welcome to the real world: Validating fixation-related brain potentials for ecologically valid settings. Brain Research, 1172, 124-129) were able to validate the FRP approach using the old/new effect. They found that this marker effect occurred earlier in FRPs than in a classical ERP setting, whereas the shapes of FRPs and ERPs were similar. In the current study two possible explanations for this finding were investigated: a preview benefit and the self-pacing of stimulus presentation. To assess these two explanations, we established four different settings. We compared a classical and a self-paced ERP experiment and two FRPs settings, where the target stimulus was either visible or masked until fixation. We found a substantially earlier occurrence of effects only in the FRP setting, where the target was already visible before fixation. The results clearly show that processing of the target was significantly facilitated when parafoveal information had been available. Therefore, FRPs indicate a substantial influence of the preview benefit, while there was no effect of the self-paced processing rate on ERPs.