The Eye Pupil Adjusts to Imaginary Light
Laeng and SulutvedtJanuary 2014
Abstract
If a mental image is a rerepresentation of a perception, then properties such as luminance or brightness should also be conjured up in the image. We monitored pupil diameters with an infrared eye tracker while participants first saw and then generated mental images of shapes that varied in luminance or complexity, while looking at an empty gray background. Participants also imagined familiar scenarios (e.g., a “sunny sky” or a “dark room”) while looking at the same neutral screen. In all experiments, participants’ eye pupils dilated or constricted, respectively, in response to dark and bright imagined objects and scenarios. Shape complexity increased mental effort and pupillary sizes independently of shapes’ luminance. Because the participants were unable to voluntarily constrict their eyes’ pupils, the observed pupillary adjustments to imaginary light present a strong case for accounts of mental imagery as a process based on brain states similar to those that arise during perception.
Our summary in plain words
What This Study Is About
How They Studied It
- Five experiments with healthy young adults, whose pupils an infrared eye tracker measured as they looked at a plain gray screen.
- Experiments 1 and 2 (17 and 18 people): people saw triangles of different brightness, then imagined each one. Experiment 2 added a run with the same displays but no instruction to imagine.
- Experiment 3 (21 people): simple or complex shapes at three brightness levels, with effort ratings. In Experiment 4, the same people tried to enlarge or shrink their pupils on command.
- Experiment 5 (52 people): imagined familiar scenes, such as a sunny sky, a night sky, a dark room, or their mother's face in sunlight or in shade.
What They Found
- In every experiment, pupils were smaller for imagined bright shapes or scenes and larger for dark ones.
- In Experiment 1, a triangle's brightness closely tracked the pupil change while imagining it (r = .80).
- In Experiment 2, the imagery effect was smaller than when seeing and needed the instruction to imagine, so it was not an afterimage.
- In Experiment 3, complex shapes enlarged pupils and felt more effortful, but brightness did not change effort; the two effects were independent.
- In Experiment 5, a sunny sky gave smaller pupils than a night sky, a cloudy sky, a dark room or a face in shade, and a dark room gave larger pupils than a night sky. Dark and bright scenes felt equally effortful.
What This Might Mean
One Interesting Detail
This summary was written with AI and may contain errors. Check the original paper.
Authors
Bruno Laeng
Department of Psychology, University of Oslo, Oslo, Norway
3 papers in the libraryUnni Sulutvedt
University of Oslo
1 paper in the library
Cite this paper
Laeng, B., & Sulutvedt, U. (2014). The eye pupil adjusts to imaginary light. Psychological Science, 25(1), 188–197. doi:10.1177/0956797613503556
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