Effects of figure context on the apparent length of a line.

This study investigated the effects of figure context on the apparent length of a line. In Exp. 1, ten participants were asked to adjust the length of a comparison line to match a standard line enclosed within a rectangle. The participants consistently overestimated the length of the standard line, demonstrating the stretching effect of figure context on the apparent length of a line. In Exp. 2 (12 participants), the size of the context figure was varied and it had no significant influence on the magnitude of the context effect. In Exp. 3 (nine participants), the context effect was shown not only for squares and rectangles but also for other shapes of figures such as circles and 5-pointed stars. We discuss the possible mechanism of the figure-context effect within Gregory's (1970, 1978) misapplied constancy theory of visual illusions.