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PLoS One. 2020 Mar 23;15(3):e0230517. doi: 10.1371/journal.pone.0230517. eCollection 2020.

Dissociable mappings of tonic and phasic pupillary features onto cognitive processes involved in mental arithmetic.

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U.S. Combat Capabilities Development Command Army Research Laboratory, Human Research and Engineering Division, Aberdeen Proving Ground, Maryland, United States of America.
Annenberg School of Communication, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
Department of Psychological and Brain Sciences, University of California Santa Barbara, Santa Barbara, California, United States of America.


Pupil size modulations have been used for decades as a window into the mind, and several pupillary features have been implicated in a variety of cognitive processes. Thus, a general challenge facing the field of pupillometry has been understanding which pupil features should be most relevant for explaining behavior in a given task domain. In the present study, a longitudinal design was employed where participants completed 8 biweekly sessions of a classic mental arithmetic task for the purposes of teasing apart the relationships between tonic/phasic pupil features (baseline, peak amplitude, peak latency) and two task-related cognitive processes including mental processing load (indexed by math question difficulty) and decision making (indexed by response times). We used multi-level modeling to account for individual variation while identifying pupil-to-behavior relationships at the single-trial and between-session levels. We show a dissociation between phasic and tonic features with peak amplitude and latency (but not baseline) driven by ongoing task-related processing, whereas baseline was driven by state-level effects that changed over a longer time period (i.e. weeks). Finally, we report a dissociation between peak amplitude and latency whereby amplitude reflected surprise and processing load, and latency reflected decision making times.

Conflict of interest statement

The authors have declared that no competing interests exist.

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