European Conference on Visual Perception edition:27 location:Budapest date:22-26 August 2004
We present evidence from asymmetric colour-matching experiments which strongly suggests that uniform surrounds evoke induction effects of a very peculiar nature, not representative of colour- induction effects in general. We compared the induction effects resulting from using a pair of uniform surrounds with those resulting from using a corresponding pair of variegated surrounds. The data curves obtained with variegated surrounds could be well described by simple von Kries scaling. The uniform surrounds, however, yielded a curious and unexpected result, namely a sharp step in the data curve indicating that a range of clearly distinguishable comparison patches were matched by identical test patches. Outside the region of this step, the data curves obtained with both kinds of surrounds were practically the same. These data can be accounted for by assuming that the induction effect observed in uniform surrounds is the result of two distinct mechanisms: a simple gain control mechanism, which is also triggered by variegated surrounds, and a contrast-coding mechanism specific to the uniform surrounds.