CONTOURS perceived in the absence of physical gradients of stimulation have been called cognitive contours1, subjective contours2,3, contours without gradients4, anomalous contours5 and quasi-perceptive margins6. The phenomenon is produced by placing inducing elements in special arrangements on a surface of uniform luminosity, as in Fig. 1. A whiter-than-white triangle can be seen overlying three black disks and a white background. The apparent brightness difference and the perceived contours extending between the disks are illusory. Gregory1 discusses two paradigms, the cognitive and the physiological, which have been used to explain these contours. We introduce here two configurations which support the cognitive paradigm.