Results of Experiment 3 (day of learning and geometric test). Bar graphs show the fishes frequency of choice (means with SEM), in terms of number of attempts in correspondence of the corridors at the geometrically correct diagonal (C1 + C2) vs. the incorrect one (X1 + X2), during the Day of learning (when fishes reached the learning criterion) (on the left) and during the Geometric test (on the right), in a transparent rectangular apparatus. As shown in the schematic drawing, the geometrically correct corners are indicated with C1 and C2 (on the same diagonal, both open during the training-phase), while the incorrect corners with X1 (near the correct C1) and X2 (near the correct C2). Black bars are referred to first choices of all fishes together, green bars to total choices of all fishes together (where there was no difference among species), yellow bars to overall choices made by zebrafish, blue bars to choices by redtail splitfin fish, red bars to choices by goldfish. Fishes learned to use geometry of the transparent arena to reorient themselves: they were able to solve the non-visual rewarded exit task, achieving the learning criterion. The geometric test confirmed that the learning effectively occurred during training, although the number of attempts among species was different in extinction of response.