Effects of Visual and Verbal Presentation on Cognitive Load in Vigilance, Memory and Arithmetic Tasks

Jeff Klingner

Stanford University

Barbara Tversky

Columbia University Teachers College

Pat Hanrahan

Stanford University

To Appear in Psychopsysiology


Degree of pupil dilation has been shown to be a valid and reliable measure of cognitive load, but the effect of aural vs. visual task presentation on pupil dilation is unknown. To evaluate effects of presentation mode, pupil dilation was measured in three tasks spanning a range of cognitive activities: mental multiplication, digit sequence recall, and vigilance. Stimuli were presented both aurally and visually, controlling for all known visual influences on pupil diameter. The patterns of dilation were similar for both aural and visual presentation for all three tasks, but the magnitudes of pupil response were greater for aural presentation. Accuracy was higher for visual presentation for mental arithmetic and digit recall. The findings can be accounted for in terms of dual codes in working memory and suggest that cognitive load is lower for visual than for aural presentation.

Figure 4: Target effect on pupil dilations evoked by heightened vigilance. Each trial of Experiment 3 had three moments at which we told participants to expect possible targets, which occurred independently at each moment with probability one half. The chart on the left shows the mean dilation in moments in which a target did not occur, and the chart on the right shows the mean dilation in moments when a target did occur. Targets elicited longer and larger pupil dilations, with a secondary peak about 1.5 seconds after target presentation. This secondary peak corresponds to the motor activity of responding to the target’s presence. Whether a target was present or absent, dilations were larger in the aural condition, and the peak dilation under aural presentation occurred about half a second later than with visual presentation.


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