SHAPE DISCRIMINATION BY RATS: SQUARES AND RECTANGLES.

Sixteen rats were trained to discriminate between a square and a rectangle: both shapes were presented in different orientations to different animals. All animals were trained in succession with positive shape only, positive and negative shapes presented simultaneously, positive and negative shapes presented successively; finally they were given tests with 18 transfer shapes presented singly. Although the rats showed a strong preference for the square early in training, they later responded more accurately to the rectangle presented on its own than to the square. There was no tendency to transfer from a rectangle in one orientation to rectangles in other orientations, and indeed when a horizontal rectangle was substituted for a vertical or vice versa negative transfer resulted. The rats (unlike octopuses) showed complete transfer to outline shapes. The transfer test results are discussed in relation to recent physiological discoveries about retinal receptive fields. [ABSTRACT FROM AUTHOR]