Capacity

• What is capacity AO1?

  Capacity refers to the amount of information that can be stored in each memory store. The capacity of sensory memory is very high. Jacobs (1887) read out increasing numbers of digits and asked participants to recall them until they can no longer remember correctly. The mean digit span was 9.3 items and for letters 7.3, suggesting this is the capacity of short term memory. Miller (1956) also found that the capacity of short term memory is around 5-9 items but can be increased through chunking. The capacity of long term memory is potentially unlimited.
• what are the strengths of capacity?

  However, by using laboratory conditions, a high degree of control over extraneous variables can be created which ensures they cannot confound the results allowing a cause and effect relationship to be established. Furthermore the standardisation of variables means they can be measured accurately, increasing the internal reliability which in turn increases the external reliability as it can be easily replicated. Moreover, other studies have replicated Jacob’s study to produce similar results, e.g. Bopp and Verhaeghen in 2005.
• what are the weaknesses of jacob’s research into capacity ?

  One weakness of Jacob’s experiment is that it uses artificial materials, so data collected may lack ecological validity as artificial conditions do not reflect real world scenarios questioning the generalisability of the results. This is because we do not remember digits like this on a day to day basis and additionally they have no personal meaning to the participants.
• what are the weaknesses of millers research into capacity?

  A limitation of Miller’s research is that he may have overestimated the capacity of short term memory. A review of research conducted by Cowan (2001) found that the capacity of short term memory was in fact much small, probably 3-5 chunks. This suggests Miller was probably only accurate towards the lower end of his estimate.