Short term and long term memory

  • Created by: emily.w.7
  • Created on: 02-02-19 11:25

What is capacity?

the amount of imformation/data that is stored in a memory store

STM-          Jacobs (87) , Miller (56)

  • aim: to find out the capacity of the STM
  • Procedure: pps were given words, numbers etc and asked to recall them straight after, acuratly and in order of presentation.
  • findings: pps could remember remember uop to 9, avg 7 and lower band being 5.
  • conclusion: STM must have a limeted capacity of 7± 2.

LTM - it has ulimeted capcity however information may be lost due to decay or interference.

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capacity cont.


from reviewing previous studies, the capacity of the STM is likely to be more limeted (to about 4 chunks).suggesting it isnt as extensive as we first thought.

Also the size of the chunk efffects how much you can remember, research has shown that people have a shorter memory span for larger chunks

It doesnt account for individual differences as the capacity for the stm isnt the same for everyone and why theese differences ocur. research has shown that recall increased steadily with age, which could be due to  an increase in brain capacity or developing strategies that help us to improve recall. 

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What is encoding?

Encoding is the way that information that enters the brain via the senses is changed so that it can be stored in memory. It can be stored in various forms eg. visually, acoustically and semantically.


Baddeley (66)

  • aim: to investigate the encoding style of the stm
  • Method: pps shown sequence of 5 words that were either acoustically simular/disimular or semantically simulr/disimular. they were then asked to write theese words down 20s after.
  • pps produced the following recall %:  10% acoustically simular, 80% dissimular, 64% semantically simular and 71% semantically dissimular. Pps confuses acoustically simular words compared to others suggesting that because they are simular and easily confused that they must be represented acoustically as part of our processing.
  • concllusion: in STM we convert visual material into acoustic code and find it diffucult to distingusih between info that sounds the same.
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Encoding cont

LTM - Baddeley (66)

  • aim: to investigate the encoding style of the ltm.
  • Method: the same as the LTM research.
  • results:pps produced the following recall % : acoustically simular and disimular words were equally poor in recall, 85% semantically simular, 55% semantically disimular.
  • when storing information in the LTM, it is better recalled if encoded semantically,


it is not clear is baddeley was actually measuring LTM as the pps had to recall the words 20 mins after which to some may not count as LTM.

Although STM seems to rely on acoustic code for stroing information, research done by other researchers has shown that visual codes are also used e.g. when verbal rehersal was prevented pps used visual codes 

LTM may not be exlusively smeantic as research done by rothbart shows evidence for acoustic coding in the LTM

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What is duration?

a measure of how long memories can be held in a memory sotre before being no longer avalible.


Peterson and peterson (59)

  • aim: to investigate the duration of the STM
  • mehtod: pps asked to rmemebr a nonsense trigram, and then gave pps a distraction task  by counting backward in sequences of 3s, they then tested the recall after 3,6,9,12,15 or18 seconds for prefect recall of the trigram 
  • after 3 seconds pps could recall about 80% of trigrams correctly, the abilty reduced to 10% after 18s.
  • conclusion: when rehersal is prevented, little can stay in the stm for longer than 18s.

the tast lacks ecological validity as the task of remebering sonsonant syllables doesnt reflect everyday memory activities.

the task does have dome relavance to everyday life as we rememeber meaningless  things such as phone numbers ect

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duration cont.


Bahrick et al

  • aim: to investigate the duraion of the LTM.
  • method:c392 graduated form an american high school over a 50 year period shown photos from their high school year book. One group of pps were given names and asked to select the photo that the name matched to and the other group were only given the photos to identify.
  • Results: name matching: 90% correct 14 years after graduation, 80% 25yrs, 75% 34yrs and 60% 47 yrs.     in the identification condition 60% correct after 7 years and 20% after 47 years.

  • conclusion: people can remeber information for almost a lifetime however acuracy can diminish over time due to decay and may be afffected by the task.

the STM results may be due to displacement of the sylables when having to count. suggesting that the results were from displacement rather than decay  and was not measuring the duration of the STM causing its validity to be low.

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