What are the three stages of memory according to the Atkinson-Shiffrin model?

The Atkinson-Shiffrin model proposes three memory stages. Sensory memory holds a large amount of sensory information for a very brief time, less than a second for visual iconic memory and three to four seconds for auditory echoic memory. Short-term memory, now often called working memory, holds about seven items, plus or minus two, for roughly 20 to 30 seconds without rehearsal. Long-term memory has virtually unlimited capacity and can store information for a lifetime.