Background articulation and relational colour constancy

A visual search experiment was performed to examine whether the detection o f constant chromatic relationships occurs in parallel. We used 6 stimulus c onditions, corresponding to different combinations of three variables, rele vant to description of displays made of different coloured regions: (i) the number of items; (ii) the number of background colour ratios; (iii) the to tal number of colour ratios. An illumination change was simulated in all tr ials. In half the trials, the simultaneous; reflectance change of one item was also simulated. When the number of colour ratios is constant, detection becomes worse as the number of items increases, as predicted by serial pro cessing of reflectance changes. However, background articulation favors rel ational colour constancy, by providing information about illumination chang es. (C) 2000 John Wiley & Sons, Inc.