The current experiment investigated ontogenetic forgetting on a novel object-recognition task similar to that of Besheer and Bevins. 18-day-old pups (n = 49) and adult (n = 29) rats were tested at two retention intervals (1 min. or 120 min.). By employing exclusion criteria which demanded minimum amounts of object exploration at training and test, the performance of 18-day-old pups but not that of adults was significantly impaired at 120 min. relative to 1 min. Analysis indicated that the ontogeny of the learning and memory measured in novel object recognition follows a developmental trend similar to that of other forms of learning, with older animals remembering more and thus performing better than younger animals. Unfortunately, given the extreme variability inherent to the task and large N necessary to achieve significance, the use of this task in studies of learning, memory, and development is discouraged.
The effects of original training-stimulus pre-test reminders were examined in a novel object recognition(NOR) task. NOR is a task that examines memory for complex stimuli, and is driven by the rats’ tendency to spend significantly more time exploring novel objects over those previously experienced. In this task, a delay is imposed between a training experience during which the animal is allowed to investigate a set of identical objects, and a later test exposure where the animal encounters one of the original objects and a novel object with which it has had no previous experience. Experiment 1 demonstrated that performance at 24 h is significantly worse than at an immediate delay (1 min). In the second experiment, it was demonstrated that neither a 10-s nor a 30-s reminder treatment, in the absence of training, resulted in a level of preference for novelty, a measure of memory for the original object, that was significantly greater than chance. Experiment 3 illustrated significant performance effects of a 30-s training stimulus reminder administered 15 min prior to test with a 24-h retention interval. The final experiment illustrated that the additional 30-s of object exposure is effective in enhancing performance only if it occurs shortly prior to test. Animals receiving the additional 30-s immediately following training did not experience such beneficial effects. It was concluded, based upon these results, that pre-test training-stimulus reminders in this task produce effects similar to those seen in more traditional tasks of learning and memory.