Abstract
The eye’s pupil typically adjusts to changes in light energy stimulating the retina. However, the pupils also adjust to imagined and illusory changes in brightness and darkness. Additionally, research has shown that the pupil adjusts differently when reading single words associated with darkness or brightness, as if anticipating actual changes in ambient light. One possible explanation is that reading a word automatically elicits a mental image or sensory-motor simulation of its meaning, which provides feedback to the oculomotor control system to adjust pupil diameter to the expected level of luminance.
To further test this idea, the present study employed eye tracking and pupillometry in a more ecological situation, such as reading a story. Participants (n=51) completed a simple reading task consisting of four short stories that included key words referencing either bright or dark scenarios. We measured relative pupil changes during reading to investigate the extent to which sensory-motor simulations of these scenarios reflected comprehension of an extended narrative.
We computed average pupil changes in each scenario and used a paired samples t-test to assess the effect of the bright and dark conditions. The results indicated that pupils constricted more in response to bright scenarios compared to dark ones. For example, pupils were larger when reading about driving into a tunnel but smaller when reading about driving on a sunny day. Using linear mixed effect models, we found that the perceived vividness of the scenes experienced modulated the effect of brightness and darkness. In essence, being immersed in a story with high vividness led to more intense pupil responses. This suggests that language input can activate sensory responses to meaning, highlighting the role of simulations and mental imagery during language comprehension.
This project was supported by a EyeHub seed grant.
Reference
Eikner, J.S., Laeng, B., Onnis, L. (2025). The eye pupils adjust to implied luminance when reading narratives. Talk presented at the Embodied and Situated Language Processing Conference (ESLP2025), Aix-en-Provence, France.
Bio:
Jason Eikner is a former master's degree student in linguistics in the Department of Linguistics and Scandinavian studies at the University of Oslo. He handed in his Master's thesis in May 2025.
Luca Onnis is a Professor of Psycholinguistics in the Department of Linguistics and Scandinavian Studies at the University of Oslo. His research explores the learnability of language, the inductive mechanisms underlying language acquisition, and the ways in which languages may shape human cognition. He is an Associate Editor of the Journal of Cultural Cognitive Science.
Bruno Laeng is professor in Cognitive Neuropsychology at the Department of Psychology, University of Oslo. Laeng is currently the Director of the Eye Tracking and Pupillometry laboratory at the Department of Psychology, University of Oslo. He is also one of the principal investigators at the Centre for Interdisciplinary Studies in Rhythm, Time and Motion (RITMO), at the University of Oslo. In 2018, Laeng was called to be a member of The Norwegian Academy of Science (Humanities and Social Sciences Division).