Episodic-like memory in non-human animals: What-Where-When memory and mental time travel.

Episodic memory is defined as a memory system that consciously carries out recollecting one's subjective past experience and re-experiencing it. Through these mental activities, episodic memory is thought to make mental time travel retrospectively and prospectively possible, which is sometimes considered to be unique to humans. However, after a seminal study in scrub-jays by Clayton & Dickinson (1998), animal models of episodic memory have been developing and are starting to affect the concept of human episodic memory itself. This paper will concentrate on reviewing the studies that could encourage nonhuman animals to utilize memory — the properties are consistent with current definition of human episodic memory. Additionally, a discussion on the possibility to divide the system of episodic memory into two sub-processes and to study in animals the sub-processes of episodic memory will be undertaken.