Contrast and assimilation in the perception of brightness

R. Shapley, R. Clay Reid

Research output: Contribution to journalArticlepeer-review


The rapid estimation of the brightness of objects is one of the nervous system's major visual tasks. Exactly how the eye and brain perform this basic task is still not understood. Two mechanisms that contribute to human perception of the brightness of objects have been identified previously: (i) the visual response to physical contrast and (ii) assimilation. Use of a unique visual display device allowed us to measure the relative importance of these two mechanisms. The present results reveal that assimilation is about half as effective as physical contrast in determining the apparent brightness of objects. These results imply that previous theories of vision - for instance, the retinex theory - will have to be revised; the importance of physical contrast must be weighted more strongly.

Original languageEnglish (US)
Pages (from-to)5983-5986
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number17
StatePublished - 1985

ASJC Scopus subject areas

  • General


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