Research into Capacity

• Research into Capacity was conducted by Joseph Jacobs who investigated digit span

  -He gave ppts 4 digits to remember and then 5 and so on until the person could not recall the order correctly
• He found the mean span for digits to be

  -9.3 items and for letters 7.3
• He also found capacity changes with age

  -mean of 6.6 for 8 yr olds and mean of 8.6 for 19 yr old
• However this research was conducted a very long time ago

  -1887 so may lack temporal validity
• George miller made observations and concluded

  -that capcity for STM is 7 + or -2
• A weakness is that Miller have overestimated capacity of STM

  -Cowan reviwed other research and concluded capacity was only about 4 chunks

  -Vogel found that 4 items were about the limit for visual items
• additionally

  -the size of the chunk matters

  -Simon (1974) found that people have shorter span for larger chunks