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Summary: Different Types of Memory

One of the earliest theories of memory during the information processing era was the Atkinson and Shiffrin model. It portrayed memory as a flow of information through three boxes, each representing a distinct memory system.

The first box consisted of the sensory stores. The sensory storage system for vision is called iconic memory. George Sperling showed that a visual image persists for a split second after stimulation.

The sensory storage system for hearing is called echoic memory. Studies indicate that it lasts for about two seconds. Other senses such as taste have split-second memory systems, too.

The second box in the classic Atkinson-Shiffrin model represents the short-term store alternatively called primary memory, working memory, and short-term memory. Working memory has at least two components: a short-lasting visual "scratchpad" and a longer-lasting verbal memory.

The longer-lasting verbal memory enables you to circulate words in your head. Rehearsal keeps information in primary memory; you just say something to yourself again and again.

The verbal portion of working memory has a limited capacity. George Miller coined the term "chunk" to describe an organized entity or thing in memory. Working memory can handle about seven chunks at one time.

To increase the amount of information in attention, one must increase the amount of information in each chunk. This can be done by organizing material into inte­grated wholes, each of which functions as one chunk.

Secondary memory, also known as long-term memory, comes in several distinct varieties. Memory for single events is stored differently from memory for general facts and knowledge.

There are at least two types of general knowledge derived from repeated experiences: declarative knowledge and procedural knowledge. Declarative knowledge is any sort of fact or information that can be declared (put into words). Procedural information involves sequences of goal-directed actions.

Memory that requires conscious processing (explicit memory) is easier to disrupt than automatic (implicit) memory. Children, drunks, and old people with dementia can have normal implicit memory, although their explicit, con­sciously manipulated memory may be impaired.

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