Visual pattern discrimination in the white rat

A theoretical discussion of Fields' results on form discrimination in white rats shows that they do not offer unequivocal evidence of visual form discrimination. Criticisms are also aimed at Fields' inadequate description of his experimental conditions. In the experiments presented in this paper a number of white rats were required to discriminate between a cross and a square of equal area and brightness presented on uniform black backgrounds. One group of 6 rats was trained in the Yerkes-Watson type of discrimination apparatus with negative results. In 1200 trials there was no sign of a learning trend. 4 of these rats and 5 new ones were given 1000 trials in a modification of Fields' apparatus. The stimuli were those used in the previous experiment. Here again there was no sign of learning. An analysis of the experimental situations involved suggests that the inability of the rats to discriminate the visual patterns was due not to the characteristics of the apparatus per se, but to a deficiency in the rat's ability to discriminate visual detail. The discrepancy between the author's results and those of Fields is ascribed to defects in Fields' procedure, defects which enable the rat to discriminate extraneous stimuli. Bibliography.