Remembrance of places passed: Spatial memory in rats

Rats were tested on an eight-arm maze in a paradigm of sampling with replacement from a known set of items until the entire set was sampled. The first three experiments demonstrated that the animals performed effi-ciently, choosing an average of more than seven different arms within the first eight choices, and did not utilize intramaze cues or consistent chains of responses in solving the task. The second three experiments examined some characteristics of the rats ' memory storage. There was a small but reliable recency effect with the likelihood of a repetition error increasing with the number of choices since the initial instance. This performance decrement was due to interference from choices rather than just to the pas-sage of time. No evidence was found for a primary effect. The data also suggest that there was no tendency to generalize among spatially adjacent arms. The results are discussed in terms of the memory processes involved in this task and human serial learning. When distinctive exteroceptive discrim-inative stimuli are consistently associated with a particular spatial location, rats pref-erentially use these stimuli for discrimina-tion learning, a phenomenon that is usually referred to as "place learning. " If place learning can be used to solve a discrimina-tion problem, rats learn very rapidly. If place learning cannot be used to solve a discrimination problem, rats learn slowly and almost invariably adopt a "position habit " or "spatial hypothesis " before find-ing the correct solution. (Relevant literature reviews may be found in Gleitman, 1955