Figure 4.

Results of experiments testing for size constancy, during which fish 2 had to discriminate between a small (S+) and a large cube. (A) Choice frequency for the small cube is plotted for different distance combinations of the objects. Below each graph, symbols show the object pair, with the object on the left depicting the S+. Numbers give the distances of S+ (first number) and S− from the gates. Distances are measured from the gate towards the edge of the object closest to the gate. Dots within each graph give mean choice latencies with standard deviation (right ordinate). N > 27 test trials per column. (B) Results of control experiments done under dim light conditions (light grey column) and in complete darkness (dark grey column). Both objects were placed 3 cm from the gates. N > 50 test trials per column.