This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Our pupils become smaller under brighter conditions and larger under darker conditions. In addition to responding to changes in light, pupil size is influenced by attention, emotion and how visual objects are perceived.
Researchers previously reported that pupils constrict more when everyday objects are perceived as glossier. But when we look at objects, we evaluate not only surface properties such as glossiness but also impressions such as attractiveness. The study investigated how these different evaluations are reflected in the timing of pupillary responses.
The study was published Sept. 1, 2026, in the Journal of Vision. Twenty-four participants 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 light, image characteristics such as the mean and variance of luminance were controlled across the set of images. In both tasks, the pupil initially constricted after an image appeared and then gradually recovered. However, the timing of this response differed by task.
When participants judged glossiness, higher ratings were associated with greater pupil constriction approximately 1 second after an image appeared. When they judged attractiveness, higher ratings tended to be associated with greater pupil dilation later. The researchers also analyzed the timing of the pupil responses using temporal principal component analysis and generalized additive models.
These analyses showed that the relationship between ratings and pupil responses varied systematically by task and over time. The findings suggest that evaluations of surface properties such as glossiness and impressions such as attractiveness may be reflected in pupil responses with different timing. "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," said Hideki Tamura, an associate professor at Toyohashi University of Technology who led the research team.
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