Workload assessment for mental arithmetic tasks using the task-evoked pupillary response

Pupillometry is a promising method for assessing mental workload and could be helpful in the optimization of systems that involve human-computer interaction. The present study focuses on replicating the pupil diameter study by Ahern (1978) for mental multiplications of varying difficulty, using an automatic remote eye tracker. Our results showed that the findings of Ahern were replicated and that the mean pupil diameter and mean pupil diameter change (MPDC) discriminated just as well between the three difficulty levels as did a self-report questionnaire of mental workload (NASA-TLX). A higher mean blink rate was observed during the multiplication period for the highest level of difficulty in comparison with the other two levels. Moderate to strong correlations were found between the MPDC and the proportion of incorrect responses, indicating that the MPDC was higher for participants with a lower performance. For practical applications, validity could be improved by combining pupillometry with other physiological techniques.