Remember when: the search for episodic-like memory in animals.

Abstract

Episodic memory refers to the rich detailed memories of events within a spatiotemporal context. It contrasts with semantic memory which includes context-free representations of facts and general knowledge. Given the frequency and severity of episodic memory deficits in humans, it would be useful to have animal models of episodic memory to better understand and treat the loss of episodic memory in humans. Some researchers have proposed that animals lack the capacity for episodic memory because of the lack of evidence for conscious self-representation in animals. However, many animal researchers have risen to the challenge and devised experiments to test various elements, features, and properties of episodic memory. The literature on episodic memory in animals is reviewed. Then three experiments examined pigeons’ memory for what events occur, where they occur, and when they occur. Two additional experiments tested the flexibility of these what-where-when memories. In Experiment 1, it was shown that pigeons had the ability to track the key location that they had to peck in order to get one of two food outcomes, which changed based on the time of day (morning or afternoon). In Experiment 2, pigeons failed to show that they could use flexibility of the what-where-when memory found in Experiment 1 in a new transfer-ofcontrol procedure. Experiment 3 and 4 examined the use of what-where-when memories in tracking food outcomes, but used how long ago events occurred rather than the time of day. The pigeons were able to use knowledge of how long ago events occurred to choose the keylight location that predicted good food rather than “rotten” or “unripe” food. Finally, in Experiment 5, the pigeons were tested on their ability to flexibly apply knowledge of “ripening” and “rotting” foods from Experiments 3 and 4 to new keylights. As in Experiment 2, the pigeons in Experiment 5 failed to show any evidence of flexibility in their what-where-when memories. Despite the results of Experiment 2 and 5, the experiments generally suggest that pigeons seem to have the basic elements required for episodic memory but may lack some of the flexibility to express those memories.