Coding, Capacity & Duration of Memory

Question 1

Outline research on the STM capacity

Answer 1

1) Jacobs
Designed the digit span technique which involved participant being given 4 digits which they had to recall in order. If they were successful they would be given 5 digits to recall and so on until the participant failed to recall the order correctly.

-mean span for digits - 9.3 items
-mean span for letters - 7.3 items
shows STM capacity limited to 5-9 items

2) Miller
- found many things of everyday practice come in 7 e.g 7 deadly sins, 7 days of the week. So, he suggested the capacity of STM = 7+/-2
- chunking items together = increases STM capacity bc easier to remember

Question 2

Evaluate research on the STM capacity

Answer 2

1) Jacobs original research doesn’t consider individual differences. For example, how STM capacity changes with age
- Jacobs later research found digit span increased with age
- mean digit span for 8yr old =6.6
- mean digit span for 19yr old = 8.6

2) Miller may have overestimated the STM capacity, as Cowan found from his research that it is limited to about 4 chunks. This suggests the lower end of Miller’s estimate (5 items) is more appropriate than 7 items.
- But, chunking can still increase STM capacity and has real-life applications e.g phone numbers

Question 3

Outline research on the STM duration

Answer 3

Peterson & Peterson’s - participants recall trigrams but to prevent rehearsal they had to count backwards from a 3 digit number
-participant had 2 practices and then 8 trials, in which retention level was different each time

RESULTS:

• longer the interval delay = less trigrams recalled
  - after 3 seconds = 80% trigrams recalled
  - after 18 seconds = 10% trigrams recalled

Question 4

Evaluate research on the STM duration

Answer 4

Limitation of Peterson & Peterson research:

1) participants exposed to demand characteristics, so results lack internal validity (explain)
- Marsh et al found STM duration was a lot shorter when participants weren’t expecting to be tested after the interval activity.

2) lacks external validity as remembering trigrams does not reflect real-life memory activities where what we are trying to remember is actually meaningful

3) difficult to distinguish between decay and displacement - interval task could’ve displaced original trigram and so act of counting backwards could be an extraneous variable
- this research could be studying the STM capacity rather than the STM duration

Question 5

Outline research on the LTM capacity and duration

Answer 5

1) Shepard tested the capacity & duration of LTM
-showed participants memorable pictures, one at a time
RESULTS:
-1 hour later, pictures shown among others = almost perfect recognition
-4 months later = able to recognise 50%
-LTM capacity & duration potentially unlimited

2) Bahrick tested duration of LTM
-participants aged 17 - 74 given high school yearbook
RESULTS (photo recognition test):
- participants within 15yrs of graduation = 90% accurate
-participants within 48yrs of graduation = 70% accurate
RESULTS (free recall test):
-after 15yrs = 60% accurate
-after 48yrs = 30%
-LTM capacity & duration potentially unlimited

Question 6

Evaluate research on the LTM capacity and duration

Answer 6

1) Shepard’s research:
- High internal validity because the experiment took place in a controlled environment
- Low external validity because the photos in the experiment meant nothing to the participants

2) Bahrick’s research:
- Low internal validity because the experiment had no control over the last time participants looked at their yearbook pictures and rehearsed the memory.
- High external validity because real-life, meaningful memories were studied

Question 7

Outline research on STM & LTM coding

Answer 7

Baddeley tested the effect of acoustic and semantic similarity on STM & LTM
-different lists of words were given to 4 groups of participants to remember:
-acoustically similar
-acoustically dissimilar
-semantically similar
-semantically dissimilar
RESULTS:
-in the recall straight after (STM recall) - participants found it more difficult to recall acoustically similar words
-STM codes information acoustically (sound)
-recall after 20 mins (LTM recall) - participants found it more difficult to recall semantically similar words
-LTM codes information semantically (meaning)

Question 8

Evaluate research on STM and LTM coding

Answer 8

1) Baddeley uses artificial stimuli to test coding in STM and LTM, so it has no personal meaning to the participants. This may make it difficult to generalise the results. So, Baddeley’s research has low external validity and limited real-world application

2) Frost found that LTM recall was related to visual, as well as semantic categories and Brandimote et al found participants use visual coding when given a visual task and are prevented from verbal rehearsal.
- This opposes Baddeley’s research as he failed to take into account visual processing for both STM & LTM