The effects of stimulus sequence on event related potentials: A comparison of visual and auditory sequences

The effect of stimulus sequence on the waveform of the scalp-recorded event-related potential (ERP) was studied in the auditory and visual modalities. The results indicate that the sequential effects are qualitatively similar in the two modalities; however, an interaction appeared between the modalities and the stimulus effects. The degree of sequential effect was a function of whether or not the stimulus eliciting the ERP was the counted (target) event. This finding is discussed in terms of an expectancy model, and the interaction is attributed to variations in short-term memory for past events as a function of the level of processing required for each.