Related Experiment Video
Updated: Jun 25, 2026

A Gaze-Contingent Display Framework for Perceptual Learning Research with Simulated Central Vision Loss
Published on: April 11, 2025
A selective deficit in the appreciation and recognition of brightness: brightness agnosia?
Tanja C W Nijboer1, Gudrun M S Nys, Maarten J van der Smagt
1Department of Experimental Psychology, Helmholtz Institute, Utrecht University, The Netherlands. t.c.w.nijboer@uu.nl
Abstract:
We report a patient with extensive brain damage in the right hemisphere who demonstrated a severe impairment in the appreciation of brightness. Acuity, contrast sensitivity as well as luminance discrimination were normal, suggesting her brightness impairment is not a mere consequence of low-level sensory impairments. The patient was not able to indicate the darker or the lighter of two grey squares, even though she was able to see that they differed. In addition, she could not indicate whether the lights in a room were switched on or off, nor was she able to differentiate between normal greyscale images and inverted greyscale images. As the patient recognised objects, colours, and shapes correctly, the impairment is specific for brightness. As low-level, sensory processing is normal, this specific deficit in the recognition and appreciation of brightness appears to be of a higher, cognitive level, the level of semantic knowledge. This appears to be the first report of 'brightness agnosia'.
Related Concept Videos
Visual Agnosia
Photoreceptors and Visual Pathways
Prosopagnosia
Anatomy of the Eyeball
Color Vision
Perceptual Constancy
Size constancy is the recognition that an object remains the same size, even when its image on the retina changes. For instance, a bus is perceived to be large enough to carry people, even if it looks tiny from...

