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Updated: May 22, 2026

Perceptual and Category Processing of the Uncanny Valley Hypothesis' Dimension of Human Likeness: Some Methodological Issues
Published on: June 3, 2013
Foveal color perception: minimal thresholds at a boundary between perceptual categories
1Laboratory of Visual Physiology, I.P. Pavlov Institute of Physiology, Nab. Makarova 6, St. Petersburg, Russia. mar.danilova@gmail.com
Abstract:
Human color vision depends on the relative rates at which photons are absorbed by the three classes of retinal cone cell. The ratios of these cone absorptions can be represented in a continuous two-dimensional space, but human perception imposes discrete hue categories on this space. We ask whether discrimination is enhanced at the boundary between color categories, as it is at the boundary between speech sounds. Measuring foveal color discrimination under neutral conditions of adaptation, we find a region of enhanced discrimination in color space that corresponds approximately to the subjective category boundary between reddish and greenish hues. We suggest that these chromaticities are ones at which an opponent neural channel is in equilibrium. This channel would be 'non-cardinal', in that its signals would not correspond to either axis of the MacLeod-Boynton chromaticity diagram.
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