IIai'vard i r H'ivci '.tily The effects of varying the interval between the conditioned and unconditioned stimuli in an avoidance learning situation have only recently been subjected to intensive experimental examination. Warner's (7) early experiment demonstrated that rats required more trials to achieve an avoidance criterion as CS-US interval was lengthened. However, there was no study of extinction, and many important indices of acquisition were not reported. Kamin's (3) recent experiment represents the first detailed analysis of the effects of the CS-US interval on the acquisition and extinction of an avoidance response. Using a trace-conditioning procedure, and CS-US intervals varying from 5 to 40 sec., Kamin found that the shorter the CS-US interval, the greater the case of acquisition and the greater the resistance to extinction. Using a delayedconditioning procedure, with a similar range of CS-US intervals, Brush, Brush, and Solomon (1) found no such marked effect from the same parameter. When the CS-US interval was held constant between the two experiments, somewhat faster acquisition and much greater resistance to extinction were found in the delayed-conditioning experiment.Although Brush, Brush, and Solomon attributed the differences between Kamin's results and their own to the difference between the trace and delay procedures, there were a number of other procedural differences between the two experiments. The CS in Kamin's experiment was the sounding of a buzzer for a maximum of 2 sec. He also used & jree-responding situation in which the dog was able to jump across the barrier at any lime. In the Brush, Brush, and Solomon experiment, the CS was the offset of the light in the dog's
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.