What This Study Is About

Aphantasia, the absence or near absence of voluntary mental imagery, is usually identified with questionnaires that rely on people describing their own experience. An earlier study reported that pupils were larger when people imagined a dark shape than a bright one, but not in people with aphantasia. It suggested this could serve as an objective test. This study tried to repeat that pupil effect and asked how reliably it tracks imagery.

How They Studied It

This was a lab experiment using an eye tracker.

50 psychology students in France took part for course credit: 48 women and 2 men, with an average age of 20.18. There was no aphantasia group. One person was excluded because the researchers suspected visual aphantasia.

Participants saw and imagined single black or white triangles while the size of their right pupil was recorded.

In one version they saw a triangle, then imagined it. In the other, a spoken word ("black" or "white", in French) told them which colour to imagine filling an outlined triangle; they saw the filled triangle afterwards.

After every trial they rated how vivid their image was on a 4-point scale. At the end they completed the QMI (Questionnaire upon Mental Imagery), which rates imagery in seven senses on a 7-point scale.

What They Found

Seeing the triangles worked as expected. In both versions, all 50 participants had larger pupils for black triangles than white ones.

Imagining them did not. In both versions there was no clear difference in pupil size between imagined dark and imagined bright triangles.

Only 56% (28/50) showed the expected pattern in each version. In the original study's group of typical imagers, 90.48% (38/42) did.

Pupil differences showed no clear relationship with QMI visual scores.

In the see-first version, the result ran against the authors' expectations. Higher vividness ratings went with the opposite pattern: smaller pupils for imagined dark triangles than for imagined bright ones. The imagine-first version showed no clear link with vividness.

What This Might Mean

The authors conclude that the pupil response is "not specific to imagined brightness" and shows "a clear lack of sensitivity to visual imagery abilities." Its use as an objective test for aphantasia is therefore "questionable." They suggest two possible reasons:

The pupil may also respond to afterimages, the colour-reversed images left after looking at something.

Their changes to the original method may have weakened the effect.

The study could not test whether the measure separates people with and without aphantasia, because no aphantasic participants were included. The sample was narrow: almost all were young women studying psychology. Each version had only 16 trials. The authors also could not confirm that participants were actively imagining throughout.

One Interesting Detail

Few participants showed the expected pattern in both versions. Of the 28 people who showed it in the imagine-first version, only 18 also showed it in the see-first version.

Research L’Année psychologique

The Effect of Imagined Brightness on Pupil Size: a Tool to Quantify Aphantasia?

Vanbuckhave and colleaguesSeptember 2026

Read the paper

Abstract
What This Study Is About
How They Studied It
What They Found
What This Might Mean
One Interesting Detail
Authors
Cite this paper

Abstract

The aim of this study was to replicate previous findings that the pupillary light response (PLR) reflects the sensory strength of imagined brightness, and to investigate the sensitivity of such a measure. Fifty French participants without aphantasia perceived and imagined a series of bright or dark geometric shapes (oriented triangles) while their pupil size was recorded. Participants’ visual imagery abilities were assessed throughout the experiment (trial-by-trial vividness ratings) and with questionnaires (Questionnaire upon Mental Imagery; QMI). In contrast to previous findings, we did not replicate the effect of imagined brightness on pupil size and found no positive relationship with self-reported vividness on trial-by-trial ratings nor with mean questionnaire scores. These results challenge the use of pupillometry to sensitively detect aphantasia. Implications for future research are discussed in the light of current theories of aphantasia.

Our summary in plain words

What This Study Is About

How They Studied It

This was a lab experiment using an eye tracker.

Participants saw and imagined single black or white triangles while the size of their right pupil was recorded.

What They Found

Seeing the triangles worked as expected. In both versions, all 50 participants had larger pupils for black triangles than white ones.

Imagining them did not. In both versions there was no clear difference in pupil size between imagined dark and imagined bright triangles.

Only 56% (28/50) showed the expected pattern in each version. In the original study's group of typical imagers, 90.48% (38/42) did.

Pupil differences showed no clear relationship with QMI visual scores.

What This Might Mean

The pupil may also respond to afterimages, the colour-reversed images left after looking at something.

Their changes to the original method may have weakened the effect.

One Interesting Detail

Few participants showed the expected pattern in both versions. Of the 28 people who showed it in the imagine-first version, only 18 also showed it in the see-first version.

This summary was written with AI and may contain errors. Check the original paper.

Authors

Claire Vanbuckhave
School of Psychology, University of Plymouth, Plymouth, U.K.; CNRS, Laboratoire de Psychologie et NeuroCognition, Grenoble, France
6 papers in the library
Nathalie Guyader
2 papers in the library
Léo Pasturel
1 paper in the library
Nicole Huson
4 papers in the library
Téo Pesci
2 papers in the library
Hélène Lœvenbruck
6 papers in the library
A. Chauvin
2 papers in the library

Cite this paper

Vanbuckhave, C., Guyader, N., Pasturel, L., Huson, N., Pesci, T., Lœvenbruck, H., & Chauvin, A. (2026). The effect of imagined brightness on pupil size: a tool to quantify aphantasia?. L’Année psychologique, Vol. 126(2), 139–157. doi:10.3917/anpsy1.262.0139

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