Lack of effect of previous undernutrition on incidental learning

Rats were either well nourished (control) or undernourished (PU) during the suckling and early postweaning periods (birth to 45 days), after which all animals were fed ad libitum. From 116 to 135 days half of the rats in each group were exposed continuously in their home cages to shape stimuli (triangles and circles). Beginning on day 136, ability to discriminate the same visual stimuli was tested by using a nonappetitively motivated version of the Lashley jumping stand technique. When the triangle was the correct stimulus during discrimination training, rats which had received prior exposure to the stimuli took fewer sessions to attain criterion performance than those which had not seen the stimuli previously. PU and control rats benefited about equally from prior exposure, indicating, in contrast to most earlier studies, that incidental learning was unimpaired by previous undernutrition. There was no effect of previous undernutrition on discrimination performance per se. Prior exposure did not improve the discrimination performance of rats trained on the circle-correct problem. Moreover, circle-correct rats tended to take longer to learn the discrimination than triangle-correct rats. These last two findings are probably related to the fact that different strategies were adopted in solving the discrimination problems. A transfer test, in which only one of the stimuli was present, indicated that rats trained on the triangle-correct problem learned almost exclusively to approach the triangle. When the circle was the correct stimulus the rats apparently learned both to approach the circle and avoid the triangle.