Episodic memory in non-humans: an approach to understand an evolutionary function of consciousness

A fundamental question in comparative cognition concerns the evolution of consciousness. It is unlikely that consciousness appeared in humans without any precursors in other animals. Yet, the concepts that dominate our understanding of consciousness are inherently human centred, focussing on subjective experiences with a rich use of language. This understanding of consciousness is probably empirically intractable in studies of non-humans. An alternative approach focuses on adopting a functional perspective. What function does consciousness serve? What can an animal capable of such a function do via its behaviour? In this connection, I review the development of animal models of episodic memory. Episodic memory involves recalling the past and in humans is described as the phenomenological conscious experience of projecting oneself (autonoesis) in time (chronesthesia). Because there are no agreed upon empirical approaches to investigate subjective experiences in non-humans, efforts to develop animal models of episodic memory have focussed on the contents of episodic memory. I review experiments using rats which suggest that, at the moment of a memory assessment, the animal remembers back in time to an earlier event or episode. I conclude by evaluating implications of episodic memory in rats as a functional window into the evolution of consciousness.This article is part of the theme issue 'Evolutionary functions of consciousness'.