Pupils respond not only to “what we see” but also to “how we evaluate it”
Distinct temporal patterns of pupillary responses during glossiness and attractiveness judgments
image:
Overview of the experiment. Left: Participants observed stimuli presented on a monitor. Right: Example stimulus.
view moreCredit: COPYRIGHT(C)TOYOHASHI UNIVERSITY OF TECHNOLOGY. ALL RIGHTS RESERVED.
＜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.
Journal
Journal of Vision
Method of Research
Experimental study
Study reveals how a membrane lipid tunes the eye’s response to light
image:
PIP2 binds to rod CNG channels and prevents cGMP-dependent channel opening, increasing rod sensitivity to dim light. Cations (blue), cGMP (light blue), and PIP2 (orange) are represented as spheres. See image below for additional details.
view moreCredit: Dr. Taehyun Park
Weill Cornell Medicine investigators have determined the mechanism by which a molecule within cells can help tune the light sensitivity of the eyes. The study identified the molecule’s binding site on a protein in retinal cells, which should enable the development of drugs that target this site to treat related eye diseases.
The study, published Sept. 3 in Nature Communications, examined the workings of the molecule known as PIP2 (PI(4,5)P2). This is a phospholipid found in the membranes of most human cells, and has a wide variety of signaling and regulatory functions. Prior research suggests that PIP2 can help tune the sensitivity of light-sensing “rod” cells in the retina by inhibiting the activation of a key ion channel called a CNG channel. But how PIP2 may do this has been unclear. PIP2’s concentration in the membranes of rod cells appears to be very low, and it is hard to measure and even harder to manipulate experimentally. The researchers used model membranes containing CNG channels and well defined PIP2 concentrations, plus high-resolution imaging techniques, to determine precisely how and where PIP2 binds to CNG channels to inhibit their activity. The results also made clear that the very low concentrations of PIP2 seen in rod cells work efficiently enough to inhibit the channel and potentially exert a vision-regulating effect.
“These findings establish a framework for understanding how lipids such as PIP2 regulate ion channel activity, and reveal the specific site where a drug could target CNG channels to inhibit their activity,” said study senior author Dr. Crina Nimigean, Distinguished Professor of Anesthesiology Research II and a professor of biochemistry and biophysics in anesthesiology at Weill Cornell Medicine.
Regulators of light sensitivity in the retina underlie the remarkable ability of animal vision to work across a very wide range of light levels—considerably wider, for example, than that of film or the semiconductor-based light sensors on modern digital cameras. PIP2’s inhibition of CNG channels in rod cells may be part of that regulatory system to help maintain optimal vision in conditions where rod cells are particularly important, namely in low-light conditions and at the edges of the visual field.
“We think that PIP2’s regulation of CNG channels is part of a natural process of tuning light sensitivity in these cells,” said study first author Dr. Taehyun Park, a postdoctoral fellow in the Department of Anesthesiology.
Understanding how PIP2 works to inhibit CNG channels also has potential clinical importance. Some forms of retinal degeneration and vision loss are caused by defective CNG channels that end up killing rod cells. In principle, a drug targeting PIP2’s binding site on CNG channels could repair the defective phenotype and ameliorate such conditions. But the structural specifics of that binding site and PIP2’s inhibitory effect have been unclear.
The scientists crafted cell-membrane-like lipid structures with CNG channels and different concentrations of PIP2, and confirmed that PIP2 effectively keeps CNG channels closed even at very low concentrations. Cryogenic electron microscopy also revealed precise structural details of how PIP2 molecules bind to these channels and hold them in a closed state.
The results overall offer the first clear and convincing picture of how PIP2 regulates rod-cell CNG channels, the researchers said.
The Nimigean lab is now following up by studying lipid regulators that help tune vision by activating CNG channels instead of inhibiting them. Their model-membrane approach, which allows precise control of any lipid constituent, also should enable progress in many other research directions, Dr. Nimigean said.
The research reported in this story was supported by a grant from the National Institute of General Medicine, part of the National Institutes of Health, through grant number GM124451.
Journal
Nature Communications
Cartoon of PIP2-mediated regulation of rod CNG channels. Illustration created with BioRender.
Credit
Dr. Taehyun Park
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