Figure 2.

Analysis of the spatial ranges of interactions in children and in adults. Performance in the contour-integration task is determined by the relative noise density (D), and it might also be determined by the absolute (cortical) spatial range of interactions. We employed new sets of cards to see whether interaction ranges limit performance. (a) Examples of cards from the new sets. (Upper Left) Contour spacing is small: 4.5 λ. (Upper Right) Contour spacing is large: 9 λ. These are partial presentations of the cards showing only the contour area; for an intermediate spacing, see Fig. 1a. (Lower) The positions of all elements in the corresponding cards. D = 0.85 in both cases. (b) Child and adult contour-integration performances as a function of contour spacing. Adult performance as defined by D at threshold does not vary significantly in the tested contour-spacing range, which means that adults are limited only by relative noise density. However, children integrate large-spaced contours with a greater difficulty, which indicates the possibility of shorter interaction ranges in their case.