Fixations, position stereotypes and their relation to the degree and pattern of stress

We have tested Maier's hypothesis that the strength of behaviour stereotypes elicited in an insoluble problem situation is a function of stress. Forty-six white rats of Wistar stock were split into two groups, which were given an insoluble problem in a water discrimination unit under two widely different degrees of punishment. Those animals who developed position stereotypes were assigned to two subgroups within each group and were given a soluble discrimination problem under conditions of 50 and 100 per cent. punishment respectively. The strength of stereotype was measured in terms of the stereotype-breaking score.

It was found that animals trained under low punishment developed the more persistent stereotypes. Animals trained under 100 per cent, punishment developed the less persistent stereotypes and the longer spans between stereotype breaking scores and the learning criterion. The behaviour of four animals in the low punishment group was closely akin to what Maier calls “abnormal fixation”; the subgroups containing them were riot unimodally distributed. Punishment differentiated response latencies which furnished evidence that the fixated animals mastered the soluble problem, in spite of not responding appropriately.