Fig. 2. Group means of fish positions in the experimental tank during chromatic stimulations. The colored bars crossing the abscissa (centre of the tank) indicate the color pairs and their orientations used for stimulation. Error bars represent S.E.M. Statistical analyses were performed using analysis of variance (ANOVA) to test for differences between groups for each color pair (Table 1) and Student's t-test to test whether group means were different from the mean in the dim-white control group (Table 2). Only statistically significant differences are indicated. *, P<0.05; **, P<0.01; ***, P<0.001. BW, bright-white rearing light; DW, dim-white rearing light.