Shape Discrimination in the Octopus and the Rat

Abstract

EXPERIMENTS on shape discrimination in rats, using the Lashley two-card jumping stand, have shown that, when rats are pre-trained to discriminate horizontal from vertical striations (horizontal positive), they tend to choose other shapes with a horizontal base-line, such as a square, triangle or pentagon, in preference to a second shape which lacks the horizontal base, such as a circle or inverted triangle. This suggests that a horizontal line in one shape of a pair which have to be discriminated from one another is isolated by the animal as a basis for discrimination; this has been verified for a number of ‘transfer’ shapes, and in each case the horizontal base was the effective element in discrimination. These experiments, reported in detail elsewhere1, were designed to overcome objections to earlier work in this field, for example, the classic studies of Lashley2.