Capacity

Capacity

1. Jacob (1887) devised a technique to measure digit span

   • the researcher have the participant a number of digits, for example 4. the participant had to learn and recall the digits in the correct order. the researcher would then read out 5 digits and so on until the participant is unable to recall. the final number of digits the participant could recall is their individual digit span. Jacob found the mean span for digits was 9.3 and for letters was 7.3
     • the study was conducted a long time ago. early research often lacked control e.g. the participant may have been distracted whilst being tested therefore did not preform as well. confounding variables like this can lower the validity of the study. however the validity of this study has been proven and other results have been confirmed in other research

2. Miller observed daily practices and noted that a lot of things came in 7 e.g. 7 days of the week, 7 deadly sins etc. this suggests the average capacity of the STM is 7(+/- 2). he also noted that people could recall 5 words as well as they could recall 5 letters. we do this by chunking the word into units/chunks.

   • Cowan (2001) combined data from previous researches and found the average capacity of the STM was 5. therefore Miller may have overestimated it.