＜Abstract＞
A research team from the Vision and Action Laboratory, Visual Perception and Cognition Laboratory, and Cognitive Neurotechnology Unit in the Department of Computer Science and Engineering at Toyohashi University of Technology, led by Associate Professor Hideki Tamura, has shown that the temporal patterns of pupillary responses differ depending on whether observers evaluate the same object images in terms of glossiness or attractiveness. The research team used images of 60 everyday objects as visual stimuli and measured pupil diameter while participants separately evaluated their perceived glossiness and attractiveness. Exactly the same set of images was used in both tasks. The results showed that higher glossiness ratings were associated with greater pupil constriction during a relatively early time window centered at approximately 1 second after stimulus onset. In contrast, higher attractiveness ratings tended to be associated with greater pupil dilation at later time points. These findings suggest that even when viewing the same objects, the temporal characteristics of pupillary responses may differ depending on what observers are evaluating.
The study was published in Journal of Vision on September 1, 2026.
https://doi.org/10.1167/jov.26.9.1
＜Main＞
Our pupils become smaller under brighter conditions and larger under darker conditions. In addition to such responses to physical luminance, recent studies have shown that pupil size is also influenced by attention, emotion, and how visual objects are perceived. The research team previously reported that pupil constriction becomes stronger when everyday objects are perceived as more glossy. However, when we look at objects, we evaluate not only visually grounded surface properties such as glossiness but also more affective impressions such as attractiveness. The present study therefore investigated how different evaluative tasks are reflected in the temporal dynamics of pupillary responses.
Twenty-four participants took part in the experiment. They viewed images of 60 everyday objects and rated, on separate 7-point scales, how glossy and how attractive each object appeared. Each image was presented for 3 seconds while pupil diameter was recorded. Because pupil size is highly sensitive to luminance, image statistics such as the mean and variance of luminance were controlled across the stimulus set.
The results showed that, in both tasks, the pupil initially constricted following image presentation and then gradually recovered. However, the temporal characteristics of this response differed depending on the evaluation task. In the glossiness judgment task, higher glossiness ratings were associated with greater pupil constriction at approximately 1 second after stimulus onset. In contrast, in the attractiveness judgment task, higher attractiveness ratings tended to be associated with greater pupil dilation at later time points. The researchers further analyzed the temporal dynamics of the pupil response using temporal principal component analysis and generalized additive models. These analyses showed that the relationship between subjective ratings and pupillary responses varied systematically as a function of both task and time. These findings suggest that visually grounded surface evaluations such as glossiness and more affective evaluations such as attractiveness may be reflected in pupillary responses with different temporal characteristics.
Associate Professor Hideki Tamura, who led the research team, commented, "Our results suggest that pupillary responses are influenced not only by the visual characteristics of the objects themselves, but also by what observers are evaluating about those objects."
＜Future Directions＞
This study focused on two types of evaluation: glossiness and attractiveness. Future research will examine other material and surface properties, such as transparency, roughness, and softness, to test how different perceptual and affective evaluations are reflected in pupillary responses.
＜Publication Information＞
Tamura, H.*, Nakauchi, S., & Minami, T. (2026). Task-dependent pupillary responses to glossiness and attractiveness judgments. Journal of Vision, 26(9):1, 1–18. https://doi.org/10.1167/jov.26.9.1
(*: Corresponding author)
＜Acknowledgments＞
This work was supported by JSPS KAKENHI (Grant Numbers JP25K21323 to H.T., JP25H01141 to S.N., and JP23KK0183 to T.M.).
Part of this work was supported by the Tokai Pathways to Global Excellence (T-GEx) program under the MEXT Strategic Professional Development Program for Young Researchers.
