A new operant discrimination test procedure for resident rats

An automated method for testing visual discrimination with water reinforcement using a modified residential Y-maze is described. The visual stimulus is presented above one of two water holes. Rats have been tested with different lengths of water periods and different intervals between the periods. During the 10 days of testing, overall activity decreased. Activity on the initial days was low during daytime, with few drinking attempts. Discrimination learning acquisition was measured as the increase in the percentage of water periods with drinking attempts in which the first attempt occurred on the correct side, and/or as the increase in the number of correct drinking attempts as a percentage of all drinking attempts. Acquisition was observed both when light indicated water and when it indicated no water. This test model may offer a useful method for standardized measurement of left/right, light on/off discriminations.