Remembering past events in chimpanzees (Pan troglodytes), bonobos (Pan paniscus) and orangutans (Pongo pygmaeus)

Abstract

Episodic memory is memory for personally experienced past events. Recently, there has been intense debate as to whether episodic memory is unique to humans, or whether it may extend to non-human animals. Although many insightful paradigms have shown elements of episodic memory in numerous species, research has been shrouded with difficulties, stemming from the extensive criteria and the phenomenological nature of such memories. This thesis, therefore, aims to move beyond a debate hindered by definition, and rather than searching for a definite answer to the question, focuses on comparing the similarities and differences between the way humans and animals (specifically, great apes) recall past events. The thesis beings with an introduction to memory, before focusing on episodic memory and the episodic memory debate. In the following chapter, the subjects (great apes) and the general testing procedure are introduced. In Chapter 3, the distinctiveness effect is investigated in the recall of a past event. The distinctiveness effect refers to the enhanced memory for distinctive, as opposed to non-distinct information. The results suggest that the distinctiveness effect occurs in great apes’ memory of past events, moreover, it occurs regardless of reinforcement, consistent with results found in humans. Chapter 4 explores involuntary memory in great apes; a form of memory that occurs frequently in humans and has been proposed to exist in animals, yet has been largely overlooked. Using a paradigm that draws upon elements of involuntary memory, apes show successful recall of a past event after long delays. Chapter 5 investigates the recall of social information from past events, an area which has received little attention. The results of this chapter indicate that apes fail to integrate social information (who) with what, suggesting that social information may not be readily incorporated into the memory of past events; however, this is likely due to a lack of saliency. The final chapter discusses the findings of the three experimental chapters (3-5), before providing potential avenues for future research.