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Fig. 13.19. Contour completion performance in closed vs. open contours. The average correlation coefficients between the MUA sequences in the complete and incomplete triangles (labeled "closed" and "open") of Figure 13.16 are shown, calculated over two trials and different groups of contour elements. Although the differences in correlation within each side are not significant (p > 0.2), the elements in the closed contour are significantly more correlated across the sides and within the whole object than in the open contour (p < 0.004), consistent with psychophysical results (Section 13.1.1). The correlations between contour and background elements and within the background were significantly weaker in both cases (p < 0.03), indicating that both contours were perceived as single objects. The PGLISSOM model therefore provides independent computational support to the theory that closed contours are salient because of proximity and good continuation rather than a special reverberatory mechanism.