The effect of prolonged exposure to visually presented patterns on learning to discriminate them.

Recent literature on the development of discrimination has shown an increasing trend toward acceptance of empiricistic explanations (2, 9). That ability to discriminate visually presented patterns develops with the experience and environmental reinforcement of the growing animal may be the case, but the evidence for this view is still inconclusive. Early studies by Lashlcy and Russell (11) and by Hebb (8) on the rat favored a nativistic interpretation of the differentiation of visual qualities, but later comparable studies with the chimpanzee and pigeon (13, 14) apparently favored an empiricistic explanation. Recent experiments by students of Hebb (5, 6, 10) have employed, an enrichment technique, with results which appear to favor a learning hypothesis. These studies attempted to provide a generally rich environment and used as criteria tests of a rather general type. If opportunity to view a varied and patterned environment is important in the differentiation of visual qualities, we do not know how general or how specific the relevant experience must be. The experiment to be reported proposed to investigate the dependence of visual form discrimination in adult rats on a specific variation in visual stimulation during growth. To this end, an experimental group of animals was raised from birth in cages which exhibited on the walls circles and triangles identical in form with ones later to be discriminated. The control group was raised under the same standard conditions but without opportunity to see these forms before the discrimination learning began. If the opportunity to view specific form,s favors development of the ability to differentiate them in a later discrimination learning problem, the experimental animals should learn faster and show a higher proportion of 5s reaching the criterion than the control group.