Elements of episodic–like memory in animals

Abstract

A number of psychologists have suggested that episodic memory is a uniquely human phenomenon and, until recently, there was little evidence that animals could recall a unique past experience and respond appropriately. Experiments on food-caching memory in scrub jays question this assumption. On the basis of a single caching episode, scrub jays can remember when and where they cached a variety of foods that differ in the rate at which they degrade, in a way that is inexplicable by relative familiarity. They can update their memory of the contents of a cache depending on whether or not they have emptied the cache site, and can also remember where another bird has hidden caches, suggesting that they encode rich representations of the caching event. They make temporal generalizations about when perishable items should degrade and also remember the relative time since caching when the same food is cached in distinct sites at different times. These results show that jays form integrated memories for the location, content and time of caching. This memory capability fulfils Tulving's behavioural criteria for episodic memory and is thus termed 'episodic-like'. We suggest that several features of episodic memory may not be unique to humans.

The Mentality of Crows: Convergent Evolution of Intelligence in Corvids and Apes

“…This finding supports the adaptive specialization of the social learning hypothesis in corvids; however, another study is more ambiguous (35). Furthermore, western scrub jays are semiterritorial, and they have highly accurate observational spatial memories (25).…”

“…Clark's nutcrackers living at high elevations cache up to 30,000 pine seeds over a wide area and can recover them up to 6 months later (24). By contrast, western scrub jays living in more temperate environments cache fewer of a wider variety of food items that differ in their level of perishability and are recovered after much shorter periods (25).…”

“…These results suggest that scrub jays remember the ''what, where, and when'' of specific caching events (episodic-like memory). This representation of the time since caching is essential for the efficient recovery of perishable food items (25,26).…”

“…For pilferers, the ability to quickly and efficiently locate caches made by others may be the difference between successful pilfering and attack by the storer. A number of corvids observe conspecifics caching and demonstrate excellent observational spatial memory for the location of another bird's caches (25,31,32).…”

Constructive anthropomorphism: a functional evolutionary approach to the study of human-like cognitive mechanisms in animals

“…The fact that caching behaviour could reveal the existence of episodic-like memory in some animals suggests that episodiclike memory may be common, but difficult to detect in animals that do not cache. Considering this possibility, Clayton et al [79] took a functional evolutionary approach (of the kind we endorse in this paper) and proposed several cases in which having an episodic-like memory may be adaptive and therefore likely to have evolved. They suggested, for example, the need to keep track of who did what and to whom in primate societies, the need of brood parasites to simultaneously monitor the breeding chronology of various potential hosts, and the need of polygynous males to keep track of the reproductive status and behaviour of their different females.…”