Long-Term Memory of Past Events in Great Apes

It has been claimed that the ability to recall personal past events is uniquely human. We review recent evidence that great apes can remember specific events for long periods of time, spanning months and even years, and that such memories can be enhanced by distinctiveness (irrespective of reinforcement) and follow a forgetting curve similar to that in humans. Moreover, recall is enhanced when apes are presented with features that are diagnostic of the event, consistent with notions of encoding specificity and cue overload in human memory. These findings are also consistent with the involuntary retrieval of past events in humans, a mode of remembering that is thought to be less cognitively demanding than voluntary retrieval. Taken together, these findings reveal further similarities between the way humans and animals remember past events and open new avenues of research on long-term memory in nonhuman animals.

A Theory About Why We Forget What We Once Knew

Traditional theories of forgetting assume that everyday forgetting is a cue-overload phenomenon, and the primary laboratory method used for investigating that phenomenon has long been the A-B, A-C paired-associates procedure. A great deal of research in psychology, psychopharmacology, and neuroscience suggests that this approach to the study of forgetting may not be very relevant to the kind of interference that induces most forgetting in everyday life. An alternative interference theory holds that recently formed memories that have not yet had a chance to consolidate are vulnerable to the interfering force of mental activity and memory formation, even if the interfering activity does not involve material similar to what was previously learned. This account helps to explain why sleep, alcohol, and benzodiazepines all forestall forgetting of a recently learned list, and it is consistent with recent work on the variables that affect the induction and maintenance of long-term potentiation in the hippocampus.

Levels of Processing and the Cue Overload Principle*

This experiment investigates the influence of processing level on the extent of Cue Overload (Watkins and Watkins, 1975, 1976) produced by semantically similar or dissimilar interpolated material. The results showed that semantically similar material only led to increased cue overload if it, itself, was processed semantically. Non-semantic processing of the same types of material failed to reveal any difference between conditions. The results are seen as supportive of the Levels of Processing approach to memory research, since they reinforce the view that different types of orienting task result in qualitative differences in the nature of processing itself. Additionally the results provide some information about the locus of cue overload effects.