This paper deals with an experiment that evaluates the effect of chlordiazepoxide (Librium) on a learning situation having a large component of punishment among the principal incentives. In recent studies by F~LDMAN (1962F~LDMAN ( , 1964) ) and FELDMAN and L~WlS (1962), it was shown that drugs in the bcnzodiazepine class, ehlordiazepoxide and diazepam (Valium), prevented the development of behavior fixations. In those studies rats were trained to respond on a Lashley jumping apparatus and then subjected to an insoluble problem which consisted of forcing the animals, by applying grid shock, to jump to one of a pair of stimulus windows (one bright, one dark) one of which was locked in a set random sequence. Thus, by chance the animals jumped to a locked window and received a bump and fell to a net 4 ft. below on half the trials, and on the other half of the trials the rats jumped to an unlocked window which opened and permitted access to a food cup on a platform in the rear. This procedure generally caused the rats to adopt a stereotyped position response which persisted during a subsequent soluble problem, but when chlordiazepoxide or diazepam was administered during the insoluble problem, a significant proportion of the animals abandoned their position stereotypes and solved the discrimination problem.
In the first experiment by I~ELDMAN (1962) one group received chlordiazepoxide only during the insoluble problem, and a second group received the drug during both the insoluble and soluble problem. In the first group 73 % of the animals solved and in the second only 40 % solved. This difference was significant only at the 10 per cent level of confidence, but suggested that the additional administration of chlordiazepoxide during the soluble problem depressed the rats' ability to solve. This suggestion was given additional support by the fact that when the drug was terminated for the second group and testing con-