The evolution of multiple memory systems.

The existence of multiple memory systems has been proposed in a number of areas, including cognitive psychology, neuropsychology, and the study of animal learning and memory.We examine whether the existence of such multiple systems seems likely on evolutionary grounds.Multiple systems adapted to serve seemingly similar functions, which differ in important ways, are a common evolutionary outcome.The evolution of multiple memory systems requires memory systems to be specialized to such a degree that the functional problems each system handles cannot be handled by another system.We define this condition as functional incompatibility and show that it occurs for a number of the distinctions that have been proposed between memory systems.The distinction between memory for song and memory for spatial locations in birds, and between incremental habit formation and memory for unique episodes in humans and other primates provide examples.Not all memory systems are highly specialized in function, however, and the conditions under which memory systems could evolve to serve a wide range of functions are also discussed.Memory is a function that permits animals and people to acquire, retain, and retrieve many different kinds of information.It allows them to take advantage of previous experience to help solve the multitude of problems with which their environment confronts them, such as how to recognize the familiar, predict events, return to particular places, and assess the consequences of behavior Recently the question has arisen as to whether the diverse phenomena of memory all depend on a single underlying system or whether they depend on multiple systems.Investigators in a number of areas, including neuropsychology, cognitive psychology, and animal learning, have argued that it is useful and perhaps necessary to postulate the existence of multiple memory systems.Several different types of evidence have been cited in support of the nonunitary view, including selective memory deficits in amnesic humans and animals, experimentally induced dissociations in normal subjects' performance of various memory tasks, and ethological observations of unusual or idiosyncratic learning abilities (e.