An experiment to explore the sensitivity of measuring mental effort by applying pupillometry and blink rate to task difficulty levels

Abstract

This empirical study investigates the feasibility of measuring mental effort through pupillometry and blink rate analysis, focusing on the applicability of widely used eye-tracking technology in realistic task environments. The experiment involved 48 participants, primarily university students, who interacted with a custom-developed version of the computer game Tetris in a controlled laboratory setting. The game incorporated systematically increasing difficulty levels, ranging from very easy to extremely challenging, enabling precise manipulation of cognitive load. Pupil diameter and blink rate data were collected using a Tobii T120 eye tracker to examine their relationship with mental effort.The findings show that average pupil diameter significantly correlates with task difficulty, allowing reliable differentiation between cognitive load levels. Temporal changes in mental effort were further explored through profile curves derived from moving-average pupil-size data, revealing fluctuations within individual task levels. Two neural network models were also trained on part of the dataset to evaluate predictive performance. Statistical analysis demonstrated limited but promising accuracy in predicting mental effort from previously unseen pupillometric data.In contrast, blink rate analysis yielded inconclusive results because the recording method and device were insufficient to accurately detect blink frequency and timing. Overall, the study supports the validity of pupillometry for assessing mental effort while emphasizing the strengths and limitations of current eye-tracking technologies in applied contexts. The results also highlight the importance of selecting appropriate measurement techniques and hardware configurations when applying physiological indicators of cognitive load in interactive digital environments and human-computer interaction research settings.

Keywords: Pupillometry, Blinking Rate, Mental Effort, Cognitive Load

DOI: 10.54941/ahfe1008220