Abstract: What is color vision for? Here, we compared the extent to which memory modulates color perception of objects and faces. Participants made color matches of stimuli illuminated by low-pressure sodium light, which renders scenes objectively monochromatic. Matches for fruit were not predicted by stimulus identity. In contrast, matches for faces were predictable, but surprising: Participants matched faces green and reported that faces looked sick. Hands and skin in masked faces were not matched green. The results suggest that the brain has a strong prior for skin color, which when violated in the face context triggers an error signal seen as greenness and interpreted as sickness. The results are consistent with a Bayesian observer in which skin-color statistics determine both encoding and decoding of sensory information. The color-matching data suggest that the face-color prior is established by visual signals arising from the recently evolved L-M cone system, not the older S-cone channel. Taken together, the results support the idea that trichromatic color plays an especially important role in social communication.
Summary: What is the function of color vision? The authors found that when retinal mechanisms of color are impaired, memory has a paradoxical impact on color appearance that is selective for faces, providing evidence that color contributes to face encoding and social communication.
The following file is available:
- Face Color Code (5.31 MB) - contains data and analysis code.
- Maryam Hasantash* (Institute for Research in Fundamental Sciences, Iran)
- Rosa Lafer-Sousa* (Department of Brain and Cognitive Sciences, MIT, Cambridge MA 02139)
- Arash Afraz (National Institute of Mental Health, NIH, Bethesda MD, 20892)
- Bevil R. Conway (National Institute of Mental Health, NIH, Bethesda MD, 20892; National Eye Institute, NIH, Bethesda MD, 20892)
*These authors contributed equally