Fig. 3. Results of transfer tests, during which the S– used during training was replaced by a novel object. Each bar depicts the choice frequency for the left object (S+) of each pair. Below each bar, the object replacing S– is named. Numbers in parentheses are the total number of each fish's choices. `Ratio' is the volume ratio of the two objects offered, i.e. volume of the right object (novel object, except for training conditions, shown in far right columns) divided by the volume of the left object (S+). (A) Fish 1 (blue) and fish 2 (red), both of which were trained to discriminate between a pyramid (S+) and a cube (S–). (B) Fish 3, trained with a cone (S+) and a pyramid (S–). (C) Fish 4, trained with an A (S+) and a mushroom (S–). (D) Fish 7 (yellow) and fish 8 (black), both trained with a cone (S+) and a cube (S–). Asterisks above each graph indicate significant differences from random choice conditions: ^*P<0.05; ^**P<0.01; n.s., non significant.