Time course of grouping of shape by perceptual closure: effects of spatial proximity and collinearity.

We examined time course of grouping of shape by perceptual closure in three experiments using a primed matching task. The gaps between the closure-inducing contours varied in size. In addition, depending on the distribution of the gaps along the closure-inducing contours--occurring at straight contour segments or at the point of change in contour direction--collinearity was either present or absent. In the absence of collinearity, early priming of the shape was observed for spatially close fragments, but not for spatially distant fragments. When collinearity was available, the shape of both spatially close and spatially distant fragments was primed at brief exposures. These results suggest that spatial proximity is critical for the rapid grouping of shape by perceptual closure in the absence of collinearity, but collinearity facilitates the rapid grouping of shape when the closure-inducing fragments are spatially distant. In addition, shape priming persisted over time only when the collinear fragments were spatially close, suggesting that a stable representation of shape depends both on collinearity and spatial proximity between the closure-inducing fragments.