Capacity

Question 1

Who carried out an experiment on capacity?

Answer 1

Jacobs, 1887

Question 2

Describe Jacobs experiment on digit span

Answer 2

The researcher read out 4 numbers for the participant to recall in the correct order.
If the order is correct then the researcher reads out 5 numbers to recall.
This continues until the participant gets the number wrong.
This then indicates an individual’s digit span

Question 3

What were Jacobs findings for digit and letter span?

Answer 3

Jacobs found that the mean span for digits across all participants was 9.3 items
The mean span for letters was 7.3

Question 4

What is ‘chunking’?

Answer 4

The capacity of the short term memory is enlarged by grouping items together

Question 5

What did Miller come up with in 1956?

Answer 5

He found out that STM capacity is:
7 +/- 2
(So 7 items, plus or minus 2)

Question 6

Give a background to George Miller’s ‘7 +/- 2 items’

Answer 6

He made observations of everyday practice - lots of things came in groups of 7. He also claimed that people can recall 5 words as easily as they can recall 5 letters. This is because we group sets of digits or letters into units or chunks - known as chunking.

Question 7

Give a strength and a limitation of Jacobs/ Miller

Answer 7

Strength - Jacob’s study has been replicated various times. Recent study’s findings have been confirmed by better controlled studies (Bopp and Verhaeghan 2005)

Limitations - Early research tended to lack control of extraneous variables. Some participants’ digit span could have been underestimated because they were distracted taking the test. This could reduce the validity of the research because of confounding variables. Cowan (2001) reviewed other research and found that STM is only about 4 (plus or minus 1) chunks. Cowan said that the lower end of Miller’s estimate (5 items) is more appropriate