The Low/High Index of Pupillary Activity

Andrew T. Duchowski, Krzysztof Krejtz, Nina A. Gehrer, Tanya Bafna, Per Bækgaard

Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


A novel eye-tracked measure of pupil diameter oscillation is derived as an indicator of cognitive load. The new metric, termed the Low/High Index of Pupillary Activity (LHIPA), is able to discriminate cognitive load (vis-a-vis task difficulty) in several experiments where the Index of Pupillary Activity fails to do so. Rationale for the LHIPA is tied to the functioning of the human autonomic nervous system yielding a hybrid measure based on the ratio of Low/High frequencies of pupil oscillation. The paper's contribution is twofold. First, full documentation is provided for the calculation of the LHIPA. As with the IPA, it is possible for researchers to apply this metric to their own experiments where a measure of cognitive load is of interest. Second, robustness of the LHIPA is shown in analysis of three experiments, a restrictive fixed-gaze number counting task, a less restrictive fixed-gaze n-back task, and an applied eye-typing task.
Original languageEnglish
Title of host publicationProceedings of the 2020 Chi Conference on Human Factors in Computing Systems
Number of pages12
Publication date2020
Publication statusPublished - 2020
EventCHI 2020 - Honolulu, United States
Duration: 25 Apr 202030 Apr 2020


ConferenceCHI 2020
CountryUnited States


  • Pupillometry
  • Eye tracking
  • Task difficulty

Cite this

Duchowski, A. T., Krejtz, K., Gehrer, N. A., Bafna, T., & Bækgaard, P. (2020). The Low/High Index of Pupillary Activity. In Proceedings of the 2020 Chi Conference on Human Factors in Computing Systems