Attneave (1954) claimed that approximations made by connecting the points of mximum curvature ( MAX points) in a picture were necessary and sufQcient for representing shapes for recognition. L o w e (1985) in turn argued that an equally sufficient representation is created by connecting points of m i n i m u m curvature ( MIN points); hence MAX points are not necessary. However, both Attneave and L o w e neglected the role of curvature concentration in their arguments. It is hypothesized here that for shapes with curvature concentrated at a small number of points, MAX point pictures are far better representations than MIN pictures. More general^,ttiemore curvature was concentrated in fewer points, the greater the advantage of MAX figures over MIN figures in recognizability. This hypothesis was experimentally verified; s o m e implications for shape representation are discussed.

This work examines the contribution of shape features to subjects' judgments of typicality for visual categories. Shape was found to make a strong contribution to typicality, as evidenced by the strong correlation between results on pictures and those on silhouettes of the same pictures. Also, di^erent measures of the contribution of shape template overlap, compactness, and number of parts - were shown to capture different aspects of that contribution. As one of the fundamental problems in category research is to determine the features used in categorization (e.g., Medin, 1989), the current work is important because it makes progress on this problem.