This chapter deals with retrieval from short-term memory and it examines an explicit logogen model of Morton. Retrieval from sensory memory may be a pseudo problem in that sensory memory could itself be simply an aspect of pattern perception. It is likely that most workers in the field would agree that four basic memory systems have been isolated: sensory memory, primary memory, secondary memory, and semantic memory, where it is understood that the first three systems are episodic in Tulving's sense. The unique experimental situation designed by Sternberg and the experiments he and others have performed with it have led to a comprehensive and influential theory of retrieval from short-term memory. The model of Atkinson and Juola serves to integrate the Sternberg memory-scanning paradigm with the more general problem of recognition. The general mechanism in their model is sort of tagging notion in which the semantic-memory location corresponding to an item receives strength marking its occurrence in an episodic context.