An inquiry into relational concepts of colour, based on incremental principles of colour coding for minimal...

Centre-surround stimuli evoke colour appearances (resembling surface colours) which cannot be produced by a single homogeneous spot of light alone (eg brown or grey). Although this seems of great impact to a general theory of colour (including 'colour constancy'), the psychophysics of these 'minimal relational stimuli' is still less well understood than often assumed. On the basis of empirical as well as theoretical observations concerning centre-surround-type stimuli we introduce a relational model of colour coding. At the core of this model is the concept of a three-dimensional linear incremental colour code which behaves differently for increments and decrements. This model takes into account results on 'discounting the background' mechanisms and it is closely related to ratio-based relational concepts and to certain opponent-colour theories. In addition, it provides an analogue to the classical distinction between light and object colours, and covers colour appearances related to object colours as well. Within the conceptual framework offered, problems of complex colour perception (eg 'colour constancy') and judgmental modes are discussed. Conclusions regarding general limitations of three-dimensional modelling in colour perception are derived and corresponding refinements of the relational perspective are briefly outlined.