Fig. 1.

Representative examples of stimulus pairs and the progression through the AST stages. This example portrays odor as the initial discriminative dimension, followed by a shift to digging medium in the ED stage. For each stage, the positive stimulus is in bold and is paired pseudorandomly across trials with the two stimuli for the irrelevant dimension. Positive (reward granting) and negative pots are placed on the left versus right sides of the arena and their position is changed throughout testing to avoid the possibility of preferred side bias.