,Coding, capacity and duration of memory
Research on capacity
Jacobs
AIM
To investigate the capacity of STM.
METHOD
• A lab experiment using the digit-span technique was conducted.
• P's were presented with a sequence of digits, followed by serial recall.
RESULTS
The average STM span was between 5 & 9 items.
CONCLUSION
The findings show that STM has a limited storage capacity of 7‡2 items.
, Evaluation of Jacob’s study
Advantages
It has been replicated:
• The study is old and early research in psychology often lacked adequate controls.
• For example, some Ps digit spans may have been underestimated as they were distracted
during testing (confounding variable).
Despite this, Jacobs' findings have been confirmed by other, better controlled studies. This
suggests that Jacobs' study is a valid test of digit span in STM.
Disadvantages
He may have overestimated STM capacity:
• Cowan reviewed other research and concluded that the capacity of STM is only about 4
(plus or minus 1) chunks.
This suggests that the lower end of Miller's estimate (five items) is more appropriate than
seven items.
Miller
He found that everyday things come in sevens:
notes on the musical scale, days of the week,
deadly sins ect. Miller thought that the span was
about 7 items plus or minus 2.
But he also noted that people
can recall five words as easily
as they can recall five letters
by chunking - grouping sets of
digits or letters into chunks.
Research on capacity
Jacobs
AIM
To investigate the capacity of STM.
METHOD
• A lab experiment using the digit-span technique was conducted.
• P's were presented with a sequence of digits, followed by serial recall.
RESULTS
The average STM span was between 5 & 9 items.
CONCLUSION
The findings show that STM has a limited storage capacity of 7‡2 items.
, Evaluation of Jacob’s study
Advantages
It has been replicated:
• The study is old and early research in psychology often lacked adequate controls.
• For example, some Ps digit spans may have been underestimated as they were distracted
during testing (confounding variable).
Despite this, Jacobs' findings have been confirmed by other, better controlled studies. This
suggests that Jacobs' study is a valid test of digit span in STM.
Disadvantages
He may have overestimated STM capacity:
• Cowan reviewed other research and concluded that the capacity of STM is only about 4
(plus or minus 1) chunks.
This suggests that the lower end of Miller's estimate (five items) is more appropriate than
seven items.
Miller
He found that everyday things come in sevens:
notes on the musical scale, days of the week,
deadly sins ect. Miller thought that the span was
about 7 items plus or minus 2.
But he also noted that people
can recall five words as easily
as they can recall five letters
by chunking - grouping sets of
digits or letters into chunks.
