Abstract
Colour vision starts in the retina where light is absorbed in three different cone classes, sensitive to long-, medium-, and short-wavelength light. The cone signals then feed into three post-receptoral channels, a luminance channel and two cone-opponent chromatic -channels. Behavioural experiments have shown that these two cone-opponent chromatic channels do not correspond to perceptually salient colour mechanisms (unique red, green, yellow, blue). The red-green mechanism, which is at equilibrium for unique yellow and blue, is approximately linear in cone space. On the other hand, the yellow-blue mechanism, which is at equilibrium for unique red and unique green, is known to be non-linear. If unique yellow and unique blue are indeed generated by a single red-green mechanism, then one would predict that the individual differences in the red and green settings are correlated; similarly for unique red and green. We tested this hypothesis by analysing the unique hue settings at different saturation and lightness levels for a large sample of observers (n=185). Our results show that the individual differences in the opponent pairs (red-green; yellow-blue) are not correlated. We have confirmed this result by analysing the data in different colour spaces (cone space, u'v'). This is inconsistent with the hypothesis that the unique hues are generated by two perceptually opponent mechanisms. We conclude that there are at least four unipolar colour appearance mechanisms.
Meeting abstract presented at VSS 2017