The determinants of illusory-contour perception.

The term 'illusory contours' refers to contours perceived where none physically exist. Three hypotheses that have been successful in their ability to account for this phenomenon invoke: (i) apparent depth; (ii) brightness contrast; and (iii) use of figural cues. An experiment has been designed to determine the extent to which each hypothesis accounts for the overall variation in subjects' responses to illusory contours when all three hypotheses are considered simultaneously. Experimental results suggest that different processes may assume a primary role in the perception of illusory contours depending upon the type of inducing area and the configuration. The results highlight the multifaceted nature of the processes involved, and indicate that no single theory can explain the perception of illusory contours.