Abstract
Changes in eye-pupil size index a range of cognitive processes. However, variations in the protocols used to analyze such data exist in the psychological literature. This raises the question of whether different approaches to pupillary response data influence the outcome of the analysis. To address this question, four methods of analysis were compared, using pupillary responses to sexually appetitive visual content as example data. These methods comprised analysis of the unadjusted (raw) pupillary response data, z-scored data, percentage-change data, and data transformed by a prestimulus baseline correction. Across two experiments, these methods yielded near-identical outcomes, leading to similar conclusions. This suggests that the range of approaches that are employed in the psychological literature to analyze pupillary response data do not fundamentally influence the outcome of the analysis. However, some systematic carryover effects were observed when a prestimulus baseline correction was applied, whereby dilation effects from an arousing target on one trial still influenced pupil size on the next trial. This indicates that the appropriate application of this analysis might require additional information, such as prior knowledge of the duration of carryover effects.
Highlights
Changes in eye-pupil size index a range of cognitive processes
While the pupil of the eye changes size rapidly to protect the cells of the retina from light overexposure (Binda & Gamlin, 2017), it is becoming clear that pupillary responses reflect a broad range of higher cognitive processes
Considering the diverging results for the prestimulus baseline correction from the other methods, we explored whether this analysis might be confounded by dilation elicited during the viewing of a preceding target stimulus, Unadjusted Pupil Size Area
Summary
Changes in eye-pupil size index a range of cognitive processes. variations in the protocols used to analyze such data exist in the psychological literature. Across the range of studies utilizing pupillary responses to index cognitive processes, variation exists in the protocols to analyze such data This raises the question of whether different approaches to pupillary response data influence the outcome of its analysis. Studies commonly performed analysis on the Bunadjusted^ area or diameter of the pupil, which was usually expressed in millimeters (Hamel, 1974; Nunnally, Knott, Duchnowski, & Parker, 1967; Scott et al, 1967) This measure is relatively easy to apply, but it has the disadvantage that individuals differ generally in pupil size and, in the degree of pupil change that they may exhibit. These factors act as a source of noise that may reduce
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