Author:

Keywords:

11 Medical and Health Sciences, 17 Psychology and Cognitive Sciences, Experimental Psychology

Abstract:

In 1954, Attneave (Psychological Review, 61, 183-193) stated that the points along the contour where the curvature changes maximally (i.e., curvature extrema) are most informative about an object's shape and identity. Apart from two informal demonstrations by Attneave (one on a random shape and one drawing of a sleeping cat), no further research has been done to support this claim. In a large-scale study (N = 161) each subject received one of four matched sets of 65 outlines, presented one by one on a computer screen. Using a computer mouse, subjects had to mark as many important points along the contour as they wished. The outlines were derived from a standard set of 260 line drawings (Snodgrass, J.G., & Vanderwart, M., 1980, Journal of Experimental Psychology: Human Learning and Memory, 6, 174-215). We then applied a smoothing technique and a saliency threshold to the dataset to eliminate noise, and varied their parameter values to examine their effects. Curvature extrema were selected most frequently, with negative minima (m-) somewhat less frequently than positive maxima (M+), especially with a relatively large smoothing parameter. Inflections were almost never chosen as salient points. The distance from a marked point to its nearest neighbor curvature singularity was shortest for more salient points, and was generally shorter for m- than for M+ points. This result implies that m- points are easier to locate than M+ points on contours of everyday objects. We will also examine the role of more global shape factors influencing the saliency of a point on an outline shape.