FIGURE 4.

Collinear flankers impair rats regardless of contrast condition. Performance of two rats in which the target contrast and the flanker contrasts were independently varied. In all cases, we measured d’ for detection of a target with collinear flankers, and subtracted the d’ we measured for the same target contrast with no flankers (reference condition). This difference (change) in d’ is indicated by arrowheads in the bar graphs. The base of each arrow is zero by definition because the flanker condition is the reference condition. (A) The reduction in detection performance caused by full contrast flankers, at four different target contrasts. (B) The reduction in detection performance caused by four different flanker contrasts, for a full contrast target. (C) All possible combinations of target contrast and flanker contrast impaired the rat’s performance. The reference condition for each comparison has no flanker present, and an equivalent target contrast. Eight of the 16 comparisons are identical to panels (A,B). Panels (A–C) show data from one subject; (D–F) show equivalent data from the second subject.