STM and LTM : Coding, capacity and duration

• What is capacity?

  The amount of information the memory store holds
• What does research into STM capacity suggest?

  Research suggests STM capacity is limited to 7+/-2 items

  -When new info comes into the STM it PUSHES OUT old information (displacement) due to this limited capacity
• What did Miller (1956)'s research show in STM capacity?

  Miller (1956) supports the idea of a limited capacity with his research using the DIGIT SPAN TECHNIQUE.

  -This involves reading a series of digit sets that get progressively longer

  -The individual is asked to IMMEDIATELY repeat the digit set back in the right order

  -Miller found that pps could recall on avg 7+/-2 digits (e.g. 5-9 items)

  -He concluded that STM 'pushes out' (displaces) the old info due to this limited capacity
• What does research into the LTM capacity suggest?

  It suggests that the capacity of LTM is UNLIMITED. As capacity of LTM is extremely difficult to measure, there's very little research in this area
• What is duration?

  Its the length of time the memory store holds information
• What does research into STM duration suggest?

  Research (Peterson and Peterson) has suggested that info can only be held in STM for a limited period of time (approx 18-30 secs)

  -However this can be extended through rehearsal (i.e. repeating the info over and over
• What did Peterson and Peterson (1959)'s research show in STM duration?

  Peterson and Peterson (1959) asked 24 students to listen to a 'consonant trigram' (random string of letters e.g. QDE).

  -Immediately after hearing the trigram they heard a random 3 digit number and they were asked to count backwards in 3s from the this number in order to prevent rehearsal of the trigram

  -They were then asked to recall the trigram after 3,6,9,12,15 or 18 seconds

  - It was found that the highest level of recall as after 3 seconds (90% recalled the trigram) but this decreased rapidly as the duration increased until there was only 2% recalled after 18 seconds.
• What did research into LTM duration suggest?

  Research suggests the duration of LTM is potentially unlimited.

  -Even if information cant be retrieved that doesnt mean the info isn't stored into the LTM
• What did Bahrick et al's (1975) research show into LTM duration?

  Bahrick et al (1975) asked 392 pps aged 17-74 to name old classmates from their high school (free recall test)

  -They were then given 50 photos, some from the pps high school yearbook, and asked if they could recognise their classmates from these photos (Recognition test)

  -They found that 15 years after graduation FREE RECALL was about 60% accurate

  -After 48 years this dropped to 30%

  -RECOGNITION was 90% accurate after 15 years, dropping to about 70% after 48 years

  -This suggests LTM could have unlimited duration and that if a long term memory cant be freely recalled, it doesn't mean its no longer stored, it may just need assistance to be RETRIEVED
• What is coding?

  The WAY INFORMATION IS PROCESSED so it can be stored in memory
• What does research into STM coding suggest?

  It suggests that encoding in STM is mainly acoustic (.e. by sound)

  -when a person is presented with a list of items to remember, they will try to hold them in STM by saying them over and over out loud.
• What did Baddeley's (1966) research show on STM coding?

  Baddeley (1966) supports this as he found that if pps were presented with a list of words that were ACOUSTICALLY SIMILAR (e.g. great, large, big) and asked for immediate recall, they then made more errors than they did when presented with a list of ACOUSTICALLY DIFFERENT words (e.g. pit , cow, few)

  -He concluded that this was because there was confusion based on the way the words SOUNDED

  -This suggests that STM encodes information acoustically
• What does research into LTM coding suggest?

  Research suggests encoding in LTM is MAINLY SEMANTIC (by meaning)

  -We need to understand something (process its meaning) for it to be retained in LTM
• What did Baddeley's (1966) research show on LTM coding?

  Baddeley (1966) supports that LTM coding is mainly semantic for he found that if pps were presented with a list of words that were SEMANTICALLY SIMILAR (e.g. great, large, big) and asked for recall 20 mins later, they made more errors than when they did when presented with a list of SEMANTICALLY DIFFERENT words (e.g. good, huge, hot)

  - He concluded that this was because there was confusion based on the meaning of the words.

  -This suggests that LTM encodes information semantically
• Evaluation of research into capacity, coding and duration in STM and LTM - Limitation

  - A problem with research into the features of STM and LTM is that the materials used are meaningless.

  -This means they don't reflect much of the kinds of information we use our STM and LTM for remembering in the real world.

  -For example remembering lists of letters, numbers or similar sounding words doesn't reflect real life memory activities where what we're trying to remember is often more meaningful and varied.

  -This is a problem as the findings may not be representative of real life STM and LTM use
• Evaluation of research into capacity, coding and duration in STM and LTM - Strength

  -A strength of Bahrick et al's 1975 study is the use of meaningful stimuli, and a methodology which is high in mundane realism.

  -This suggests that the findings have high ecological validity because they can be easily generalised to real-life, due to the stimuli reflecting those which we would often try to learn and recall in our day to day lives: information with personal and meaningful value