Tilt discrimination in the mouse.

We tested the visual discrimination of mice in a two-choice discrimination box. After reaching criterion in a brightness discrimination the animals were trained on an orientation discrimination (vertical vs horizontal). Training was continued with the discrimination of vertical striations (S+) vs oblique ones (S-) of 10 different angles (80 to 15 degrees). The tilt discrimination for the last 5 days of training we found to be 30.5 (S.E.M. 3.2) degrees in albino and 19.9 (S.E.M. 0.7) degrees in pigmented mice. This is much higher than the 9.55 (S.E.M. 0.95) degrees found in pigmented rabbits but is comparable to the 17 degrees found in hooded rats by others.