The Index of Pupillary Activity: Measuring Cognitive Load vis-à-vis Task Difficulty with Pupil Oscillation

Andrew T. Duchowski, Krzysztof Krejtz, Izabela Krejtz, Cezary Biele, Anna Niedzielska, Peter Kiefer, Martin Raubal, Ioannis Giannopoulos

2018 W: Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems / Mark Perry, Anna Cox, Regan Mandryk, Mark Hancock; New York: Association for Computing Machinery, Article No 282

2018 CHI Conference on Human Factors in Computing Systems. Montreal, 2018-04-21 - 2018-04-26

A novel eye-tracked measure of the frequency of pupil diameteroscillation is proposed for capturing what is thought to bean indicator of cognitive load. The proposed metric, termedthe Index of Pupillary Activity, is shown to discriminate taskdifficulty vis-à-vis cognitive load (if the implied causality canbe assumed) in an experiment where participants performedeasy and difficult mental arithmetic tasks while fixating a centraltarget (a requirement for replication of prior work). Thepaper’s contribution is twofold: full documentaton is providedfor the calculation of the proposed measurement which can beconsidered as an alternative to the existing proprietary Index ofCognitive Activity (ICA). Thus, it is possible for researchersto replicate the experiment and build their own software whichimplements this measurement. Second, several aspects of theICA are approached in a more data-sensitive way with the goalof improving the measurement’s performance.