The world and our representations of it contain coherent objects and continuous surfaces. While, the input from the world to our eyes is spatially and temporally fragmentary. How do visual processes overcome this fragmentation to achieve accurate object perception? Shipley & Kellman (1994) found that limited temporal window governed the boundary formation process. Unuma & Hasegawa (2002) also studied the role of visual buffer in the spatiotemporal contour interpolation. While, Ringach & Shapley (1996) investigated spatial and temporal properties of illusory contour perception.

We hypothesized that illusory contour interpolation between spatially and temporally fragmental elements could occur in a particular temporal span suggested in the previous studies. Specifically, we conjectured that if elements are integrated and produce a shape in the hypothesized temporal range, the performance of shape discrimination task should be better than those with fragmental elements. The method of constant stimuli was used. We measured the psychometric functions for the discrimination of the shape as a function of presentation cycle of inducing figures.

Results show that discrimination of illusory contour shape was enhanced in the hypothesized temporal span. The threshold for illusory shape discrimination was compared to those in the control condition for local edge orientation discrimination, and the threshold for illusory contour was significantly lower than those for the edge orientation. These results support the notion that visual edges can be interpolated in the limited temporal span. Moreover, these suggest that contour interpolation in spatiotemporal domain could be used to improve shape discrimination performance greatly.