Memory

• Capacity 


  Measure of how much can be held in memory. It is represented in bits of information such as number of digits recalled.
• Short term memory (STM)

  Your memory for immediate events. STMs are measured in seconds and minutes. Disappear unless rehearsed.
• Long term memory (LTM)

  Your memory for past events. anywhere from 2 minutes to 100 years. LTM has potentially unlimited duration and capacity and tends to be coded semantically
• The capacity of STM - digit span

  Joseph Jacobs (1887) used digit span to assess STM capacity. He found the average span for digits was 9.3 and for letter 7.3

  It was easier to recall digits as there are only nine digits whereas there are 26 letters.
• The magic number 7±2 , article by George Miller (1956)

  He reviewed psychological research on immediate memory span. He concluded the average span was about 7 items (sometimes a bit more or less). People could count 7 Dots flashing onto a screen, not many more. Miller also found we can recall 5 words as well as 5 letters- we can chunk things together to remember better
• A03 capacity, Capacity of STM may be even more limited 


  • Millers original studies never replicated
  • Cowan (2011) reviewed many STM capacity studies. Concluded STM is more likely limited to 4 units
  • Voge et Al (2001) also found this when research storing visual information
  • Miller's research still somewhat appropriate( at the lower end of 5)
• A03 of capacity, the size of the chunk matters

  • Simon (1974) people have a larger memory span for large chunks, e.g an 8 word phrase rather than smaller chunks e.g: a one syllable word
  • Reaffirms STM is limited
• A03 capacity, individual differences

  • Everyone's STM capacity is different.
  • Jacobs found recall ability increased steadily with age. 8 year olds could only remember 6 digits
  • This so due to the change in the brain's category &/or the development of strategies like chunking
• LTM potentially lasts forever but STM doesn't last very long. Unless you repeat the items over and over again.
• The duration of STM

  Petersons (1959)

  • 24 students each tested on 8 trials. Each trial ppt given a trigram and digit number (e.g: THX 321)
  • asked to recall trigram after intervals between 3-18 seconds.
  • During the interval , asks to count back from their number.
  • Then recall trigram
  • 90% able to remember after 3s. Less able as time increased. By 18s only 2% could recall correctly
• The duration of LTM study Aim? (Bahrick et Al 1975)


  To see if LTM exists, if it's effected by recognition of free recall.
• Procedure of Bahrick et Al's test on duration of LTM

  • 400 graduates asked to recall classmate's names after being showed pictures. Another group asked to recall names without pictures
  • One group graduated 15 years ago and the other 48 years.
• Findings of Bahrick et Al's study on duration of LTM

  • In photo recognition condition 90% correct after 15 years and 60% correct after 48
  • In recall group 60% correct after 15 years and less than 30% after 48
• Conclusion to Bahrick et Al's study on LTM

  People can remember certain types of information for a lifetime. LTM Is better through visual recognition
• A03 of duration, Testing STM is artificial (Petersons study)

  • Trying to recognise letters doesn't reflect everyday , meaningful memory activities
  • However, we sometimes try remember things seeming meaningless such as phone numbers. So the study has some everyday relevance.
• A03 of duration. STM results may be due to displacement

  • Arguably, Petersons study didn't exactly measure what it set out to
  • Ppts were counting the numbers in their STM which may displace/overwrite the syllables to be remembered.
  • Reitman (1974) used audio tones and found STM was lower
• Coding (memory)

  Information has to be stored into the memory. It is held in the forms of sounds(acoustic), images (visual) or meaning (semantic)
• Acoustic and semantic coding

  • Words like cat ,cab and can are acoustically similar but semantically different
  • Words like great, big and large are the opposite.
  • Alan Baddeley (1966) uses similar words to test acoustic & semantic similarity on STM & LTM.
  • Ppts struggled with acoustic in STM but not in LTM
  • It was the complete opposite for semantic
• A03, coding. STM may not be exclusively acoustic

  • Bradimote (1992) found ppts used visual coding in STM
  • Ppts shown picture and prevented from using acoustic coding.
  • And so ppts used visual coding
  • Other research has also shown semantic coding is used
• A03 of coding. LTM may not be exclusively semantic

  Frost (1972) showed that long term recall was related to visual coding & semantic.

  Nelson & Rothbort (1972) found evidence of acoustic coding in LTM

  Coding in LTM isn't exclusively semantic, but varied
• A03 of coding. Baddeley may not of tested LTM

  Baddeley's method criticised. Participants LTM was tested after 20 minutes. Arguably this is not really the LTM
• Influence of STM

  Bower & winzen(1969) Digit strings within a series of trials , became progressively easier for ppts to recall as STM capacity temporarily increased
• Ways of improving recall


  • Reading aloud improves recall compared to subvocal repetition
  • Rhythmic grouping: grouping numbers together rhythmically (e.g: singing)
• Maintenance rehearsal effecting duration

  Items disappear from STM if rehearsal is prevented. New items take their place as existing items move on.
• Deliberate intention recall affecting duration 


  Information can vanish from STM in seconds if people don't try to retain it
• Sensory memory/sensory register (SM/SR)

  Temporary storage systems that hold relatively unprocessed information for fractions of a second. After stimulus is no longer available information is forgotten.
• Duration 


  How long a memory lasts before it's unavailable
• Sensory memory is information held from all sense (smell, touch ect). We are constantly receiving information that disappears if we don't pay attention
• The capacity of the SM is unlimited. Amount of information processed is highly detailed and ever-changing
• Evaluation of SM capacity

  • SM research is artificial so lacks mundane realism
  • Capacity of iconic store well researched, other stores need more research
• Coding in SM

  Information stored in a raw, unprocessed store. With separate sensory stores for each sense
• Research for coding in SM (Crowder 1993)

  Found the SM only retains information in its iconic store for a few milliseconds but for 2-3 seconds within the echoic store, suggesting separate stores as well as varying durations
• Evaluation of coding in SM

  Sensory memory could consist of several sub-stores within the main stores. More research needed in this area
• Duration of the SM

  • Duration is limited in all the SM stores
  • Each store decays at different rates
  • Different sensory stores have different duration rates
• Research of duration of the SM (Walsh and Thompson 1978)

  Iconic store has an average duration of 500 milliseconds, decreasing as individuals get older. Duration is limited & age dependent
• Evaluation of duration of the SM

  Evolutionary perspective suggests the brief duration of sensory memory allows people to focus on what they need to & and forget what they don't need.
• Stage 1 of the multi-store model of memory (MSM)

  The sensory register

  External stimuli that enters sensory memory. The capacity of these registers is large but will decay if it doesn't receive attention

  Key process, Attention - if you pay attention stimuli will pass to the STM
• Store two of the MSM

  Short term memory (STM)

  Immediate tasks e.g: someone's coffee order. STM duration is limited and the capacity is small so memory will decay or be replaced unless we repeat the information to remember It. This is called maintenance rehearsal

  Key process, Maintenance rehearsal- STM memories are rehearsed/repeated then pass to LTM.
• Store 3 of the MSM


  Long term memory (LTM)

  unlimited in duration and capacity. You may feel you have forgotten things but in fact they are lost in the LTM store. You must retrieve them

  Key process, retrieval - the process of getting information from the LTM. Information passes back into the STM and then is available for use
• Atkinson and Shiffrin (1968,1971) created the multi-store model of memory (MSM). It shows how information flows through the three memory stores.