Research on capacity

• Research on Capacity

  Capacity- the amount of info that can be held in a memory store.

  Digit span- Jacobs (1887) developed technique to measure digit span. E.g. gave ppts 4 digits to recall in order out loud, then 5, until they couldn't. Mean span for digits= 9.3 items. letters= 7.3

  Span of memory and chunking- Miller (1956)- The span/capacity= 7 +/- 2. But recall 5 words as well as they recall 5 letters- They do this by chunking- grouping sets of digits or letters into units or chunks.
• Research on capacity- evaluation

  Jacobs- conducted a long time ago, early research often lacked adequate control. E.g., distracted when tested. Confounding variables = results might not be valid. But results have been confirmed by other research.

  Miller- may have overestimated capacity for STM. E.g., Cowan (2001) reviewed other research and concluded that capacity was only about 4 chunks- means lower end of estimate (5 items) is more appropriate.