coding, duration and capacity of memory stores

capacity

how much information is held in a memory store

duration

how long information can be held in a memory store

duration and capacity of long-term memory

capacity- unlimited

duration- UP TO a lifetime

duration and capacity of short term memory

duration- less than 30 seconds

capacity- very limited, 7 ± 2 chunks of information

results of jacobs (1887) capacity of STM study

capacity of STM was 9.3 numbers/ 7.3 letters

outline jacobs (1887) capacity of STM study

used digit span technique to assess capacity

results of Miller (1956) capacity of STM study

meta-analysis found capacity of STM was 7± 2 chunks (didn’t matter if single letters or words)

results of Peterson and Peterson (1959) duration of STM study

on average 90% correct after 3 seconds, 20% correct after 9 seconds, 2% after 18seconds

found duration of STM is 18seconds

outline Petersons and Petersons (1959) study on duration of STM

participants read out a trigram which then they had to repeat, they were then given a three digit number they needed to count backwards from in 3s for 3,6,9,12,18 seconds and then participants where then asked to recall the trigram

results of Bahrick et al (1975) duration of long-term memory study

participants who were tested within 15 years of graduation were about 90% accurate in photo recognition task and 60% accurate in free recall. 48 years after graduation photo recognition was still about 70% and free recall was 30% accurate

concluding duration of LTM can be many, many years

outline Bahrick et als study on duration of LTM

participants were asked to name their graduating class (free recall)

participants were shown 50 photos (some of which were from their high school year book)

results of Baddeley study (1966) coding in LTM and STM

when asked to recall immediately after hearing the words they did better when the words were acoustically different and when asked to recall 20minutes later they did better when words were semantically different

Baddeley found that SMT codes acoustically and LTM codes semantically

is LTM acoustic or sematic

semantic

is STM acoustic or sematic

acoustic

outline Baddeleys study on the coding of STM and LTM

heard one of the following lists of words

• acoustically similar (sound similar)

• acoustically different

• semantically similar (same meaning)

• semantically different

evaluate the use of these studies to determine features of the STM and LTM

• lack of ecological validity- uses artificial and meaningless stimuli e.g. numbers or words, our memories may work different in real life with more meaningful information so we may not be able to generalise the results to how our memories work in real life

• lack of internal validity- research is old and so scientific principles of careful control and standardisation were not always in place meaning confounding variables may have affected results

evaluate Bahrick et al study

• high in ecological validity- studied duration of LTM using natural stimuli (people participants went to school with) so is an example of our memories working in real life situations so we can generalise the results to real life

• lack of internal validity- due to real life nature of study extraneous variables can not be controlled, e.g. participants who were more sociable back in high school are more likely to remember more people than participants who were more conserved, These variables will affect the results