Comparative Mental Time Travel: Is There a Cognitive Divide between Humans and Animals in Episodic Memory and Planning?

Abstract Mental time travel is defined as the human ability to remember unique personal past experiences (episodic memory) and to anticipate and plan future events. Considerable debate has arisen around the question of whether nonhuman animals are also capable of mental time travel, ranging from complete denial of the ability in nonhumans to the suggestion that they have episodic memory and readily plan for the future. We evaluate the current evidence available from comparative cognition experiments and human-developmental research. Studies of episodic-like memory in birds and nonhuman mammals have centered on their ability to remember what, where, and when a single event occurred. Although clear evidence for memory of what and where has been shown, memory of when does not always appear and may depend on both the species tested and the experimental design used. We argue for a clear distinction between remembering when in absolute time an event occurred and remembering how long ago it occurred. Studies of neural processes indicate that the hippocampus is necessary for episodic memory in humans and episodic-like memory in rats. It is argued that studies of nonhumans should not focus on presence versus absence of human traits but should examine alternative mental time travel abilities in animals that may have evolved independently as adaptations to a particular ecological niche.