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Joris Vincent, Steven L. Buck; Is Brown Induction Just Brightness Induction?. Journal of Vision 2016;16(4):32-33. doi: 10.1167/16.4.30.
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© 2017 Association for Research in Vision and Ophthalmology.
A yellow stimulus surrounded by a sufficiently bright context will appear darker, but also categorically shift to brown. Is this brown induction modulated by features of the surrounding context (such as the luminance, area, duration) in the same way as brightness induction? Here we directly compare contextual modulation of achromatic brightness to the strength of brown induction using White's illusion, which causes two physically identical targets to differ in brightness.
Six participants matched the brightness of two achromatic targets in White's illusion. On average, participants adjusted the luminance of the two targets in a 1.76:1 ratio (SD = .38) to produce a brightness match.
Participants also adjusted both targets to the highest light level at which they looked pure brown (and not a mix of brown and yellow). On average, participants adjusted the luminance of the two targets in a 1.31:1 ratio (SD = .25) to produce these brown boundaries, in the same direction as the achromatic White's effect. The brown boundary ratios were smaller than predicted from regression of participants' brightness matches, and smaller than participants' actual achromatic brightness matches in their brown boundary range.
These results suggest that while White's illusion is very successful at producing consistent brightness differences for achromatic and brown stimuli, but the analogous White's effect produced for brown induction is smaller than expected from brightness matching. This indicates that brown induction is not a simple translation of brightness induction into the chromatic domain.
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