Interrelationships among auditory and visual cognitive tasks: An Event-Related Potential (ERP) study

Abstract

The two studies presented here used event-related potentials (ERPs) to investigate relationships among three elementary cognitive tasks (visual and auditory inspection time and pitch discrimination). This article focuses particularly on contrasts between subgroups with high and low threshold. In one study the participants ( n = 29) performed both auditory inspection time (IT) and pitch discrimination tasks. In the second study, participants ( n = 35) performed a visual IT task. ERPs were obtained during performance of these tasks, and related to measures of the participant's IT or pitch threshold (PT) and intelligence (Raven's APM or Alice Heim 5 Test). The article gives details of a new bootstrap procedure to obtain confidence intervals for ERPs from subgroups differing in threshold or IQ. The ERP waveform contained regions in which individual differences could be related to IT or pitch thresholds. For both visual and auditory IT, the threshold-related part of the waveform fell around 150 to 160 ms after stimulus onset, in the rising phase of the P200 component. In the pitch discrimination task threshold-related differences occurred later, from the peak of the P200 component onwards (200–300 ms after stimulus onset). The ERP results imply that, despite a substantial correlation (+.45) between auditory IT and PT thresholds, different aspects of the stimulus-processing mechanism are critical in these two auditory tasks. In contrast, both IT tasks—which were united in emphasising speed of intake, despite the differences in the stimuli involved—were linked by the ERP results. Some investigators have concluded that pitch sensitivity rather than speed of stimulus intake is tapped by the auditory IT task. The ERP data contradict this view, and lend support to an analysis by Deary (1994b) that distinguished “speed” and “pitch sensitivity” factors in auditory tasks. Intelligence-related differences were found in the VIT-task ERPs around 100 and 150 ms after stimulus onset, but individual differences the auditory-task ERPs showed little relationship to RAPM score. Several factors may underlie this difference in the results for auditory and visual tasks.