The strengths of simultaneous colour contrast and the gamut expansion effect correlate across observers: evidence for a common mechanism.

We present the results of an experiment aiming to clarify the relation between simultaneous colour contrast and Brown and MacLeod's (1997) gamut expansion effect. These two context effects are often thought to be due to two different mechanisms, but this assumption has not previously been subjected to empirical test. Here we used inter-individual variability in the susceptibility to these effects to test this assumption. The individual variability was found to be quite substantial for both context effects. As would be expected if a common underlying mechanism contributes to both effects, a significant correlation across observers was found. It is suggested that this putatively common mechanism of 'crispening' accounts completely for the gamut expansion effect, and partially for the simultaneous colour contrast effect, which seems to depend on von Kries adaptation also.