Figure 6. Structural discrimination learning, Stages 4–6. Mean performance of the perirhinal lesion (PRh, square) and sham control (Sham, circle) groups. The upper graphs show performance on the third (new) discrimination (H|B vs. B|H). The lower graphs show concurrent performance on the previous two structural discriminations (Tasks 1 and 2). In Stage 6, all three discriminations were equally intermingled within a session so that the rats had to solve the full configural task. The vertical bars show the standard error of the mean (although when small, they are obscured by the symbols). B = black; H = horizontal; W = white.