The function of episodic memory in animals

Abstract

The best-known example of episodic memory in animals came from food-storing birds. One of the beauties of the food-storing system was that inherent in the behaviour were the elements that (at the time) made up episodic memory: what, where and when. While there were then already plenty of data on animals' ability to put together what and where, the addition of the time element in animals' memory and its testing was one that was both new and experimentally challenging. It has, however, led to an increasing variety of examples showing that animals can put together all three informational components. If episodic memories can be described as those memories that make any one of us who we are, why should non-human animals have such memories? Here, we argue that episodic memories play a significant functional role in the lives of real animals, in particular, enabling them to make decisions about how they might or should act in their future. We support our argument with data from a range of examples, focussing on data from the field.This article is part of the theme issue 'Elements of episodic memory: lessons from 40 years of research'.

Keywords: episodic memory; natural selection; what–where–when; what–where–which; wild.

Figure 1.

In the upper panel is a schematic showing an array of eight artificial flowers, arranged in two squares. The colour patterns of the flowers and their relative position in each of the sets of four flowers were the same. The lower panel, labelled AM training, shows the categorization of the type of visit a hummingbird might make to each of the flowers. Only one flower contained the reward (the correct flower), and visits to the other flowers were categorized as what, where, when or all wrong errors. From Marshall et al. [27].

Figure 2.

In the upper section is a schematic from the visual condition of the Jelbert et al. [28] experiment. Each board was coloured with a different colour pattern and only one of the four flowers on each contained reward. On the board labelled background 1, the correct (i.e. the one containing reward) flower was the pink one on the top of the board, whereas on the board labelled background 2, the correct flower was the green one at the bottom of the board. In the lower section is a schematic showing the sequence of presentation to the hummingbird: once the bird had fed from the feeder, the first whiteboard was presented. On this board the orange flower at the bottom contained reward, while on the board that followed the bird would find reward only in the purple flower at the top of the board. The feeder would then be returned and the next trial would begin. From Jelbert et al. [28].