The usual investigation of drug effects proceeds along the lines of animal investigation followed by subsequent clinical evaluation. For example, the methodology for evaluating the effects of "tranquilizers" most frequently begins with experiments of the effect of a drug (a) on the prolongation of sleeping time of animals, (6) on the taming of vicious animals, (c) on activity measures on animals, and (d) on the various conditioned avoidance responses of animals. The clinical evaluation usually takes the form of administering the drug to patients, often in settings such as a hospital, where extraneous variables are difficult to control. It would appear that in the case of the tranquilizing agents the step immediately subsequent to animal investigation and before the clinical trial should be a laboratory investigation using human Ss under controlled conditions of induced stress. The present study is directed toward the experimental investigations of the effects of certain drugs on a psychomotor task under conditions of an anxiety-producing nature. Specifically, the purpose was to test and, if possible, differentiate between the effects of meprobamate, chlorpromazine, pentobarbital, and a placebo on a behavioral task performed by human Ss under a contrived stress-producing situation. (PsycINFO Database Record (c) 2006 APA, all rights reserved)