Acquired distinctiveness of cues in the pattern discrimination learning in the white rat

Abstract

LAWRENCE (5) found in his experiment that in discrimination learning rats used the cue which had been relevant in the preceding learning situation more than that which had been irrelevant. From these findings he concluded that the rats learned to respond to the relevant cue and to ignore the irrelevant one. The present experiment was designed to investigate the functions of the stimulus dimensions which were previously relevant, irrelevant and constant, testing the above conclusion.Apparatus LASHLEY'S jumping stand painted grey.Stimulus Cards Nine sorts of black-and-white stripes varying in two dimensions : direction (vertical, oblique and horizontal) and width (1.5 cm, 1.0 cm and 0.5 cm).Procedure The one employed by LAWRENCE with two supplemental groups was followed. Four groups of animals were given a successive discrimination problem with a pair of stimulus cards, in which the direction of the stripes was relevant and the width was irrelevant for animals in Group A I, and the relation was reverse for Group A II and the direction was relevant and the width was kept constant in terms of the intermediate value for Group B I, and the relation was reverse for Group B II.They were then given a simultaneous discrimination problem in which both dimensions were relevant for all animals. This was followed by two tests of cue-distinctiveness, cue-opposition and cue-reduction.Results 1. In Group A the stimulus dimension which had been relevant in the preceding learning proved to be a little more distinctive in the proceeding learning than that which had been irrelevant, but the difference was not statistically significant. 2. In Group B the stimulus dimension which had been relevant was much more distinctive than that which had been constant.Conclusions 1. The rats learned to respond to the relevant stimulus dimension. 2. It is doubtful whether the rats learned to ignore the irrelevant dimension, but it is likely that it might have possessed certain distinctiveness as a cue.