A new phenomenon from rotating colours

This paper describes a colour effect first observed by Spillman (1974) and described by Davidoff, Aspinall, and Hill (1977). Two discs of 15 cm diameter consisting of the ten major Munsell colours in spectral order at value and chroma 6 were rotated. The discs were placed in a viewing chamber with neutral walls lit by either illuminant A or C and viewed by observers from a distance of 2.5 m. Observers were asked to match the perceived disc to a colour circle containing caps 1-85 from the 100 hue test set in an adjacent chamber under illuminant C. Normal observers: Forty subjects gave predominantly yellow-blue matches for clockwise rotation and red-green matches for anticlockwise rotation. Colour defectives: (a) Six protanopes and three deuteranopes had mean matches for red-green and yellow over 3 sigma away from those of normals, while the blue response was indistinguishable from normal. (b) Three protanomalous and eight deuteranomalous observers gave normal responses to the yellow-blue disc, but abnormal to either red or green (particularly green) in the red-green disc. (c) Protanopes and deuteranopes saw both discs as identical and named both yellow-blue. The saturation of rotating elements was stronger than stationary ones. The effect was strongest under tungsten light. Reduced angular size appeared to enhance the effect. Eccentric viewing appeared to enhance the effect. The effect appeared optimal at 10 cycles/sec. The effect disappeared at high illuminances (~ 2000 lux). The spatial configuration of colours was unstable. Re-arranging the order of colours on the disc destroyed the effect.