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.