Cognitive Revision Notes

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Short Term Memory
Description Key Study
Peterson and Peterson (1959)
Duration Between eight and thirty seconds
Trigram experiment
Miller (1956)
Capacity Seven items (± two items)
Magic number seven digit span task
Baddeley (1966)
Encoding Mainly acoustic (sound based)
Immediate recall study
Peterson and Peterson (1959)
o A lab experiment was conducted in which 24 participants had to recall trigrams
o To prevent rehearsal participants were asked to count backwards in threes or fours from a
specified random number until they saw a red light appear
o Participants were asked to recall trigrams after intervals of 3, 6, 9, 12, 15 or 18 seconds
o The longer the interval delay the less trigrams were recalled
o Participants were able to recall 80% of trigrams after a 3 seconds delay
o However, after 18 seconds less than 10% of trigrams were recalled correctly.
o Short-term memory has a limited duration when rehearsal is prevented
o The results of the study also show the short-term memory is different from long-term
memory in terms of duration
o This experiment has low ecological validity as people do not try to recall trigrams in real
Miller (1956)
Miller's (1956) Magic number 7 provides evidence for the capacity of short term memory
He though that short term memory could hold 7 because it only had a certain number of "slots" in
which items could be stored
However, Miller didn't specify the amount of information that can be held in each slot
We can "chunk" information together we can store a lot more information in our short term
Miller's theory is supported by evidence from various studies, such as Jacobs (1887).
o He found out that people find it easier to recall numbers rather than letters. The average
span for letters was 7.3 and for numbers it was 9.3.
o Lack of ecological validity due to artificial task and setting
o Vogel et al. (2001) suggested that the capacity may be closer to four items for visual items
Baddeley (1966)
o Participants were split into four groups, each of which had to listen to a group of five words
o The words were either acoustically similar or dissimilar, semantically similar or dissimilar
o They were asked to immediately recall the words in the same order

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The procedure was repeated four times
o The results showed that it was much harder to recall acoustically similar words than
dissimilar words and that the meaning of words had less significant difference to recalling
o Encoding in STM is acoustic (sound based)
o Encoding in LTM is semantic (meaning based)
o Brandimonte et al. (1992) challenged his findings by finding that visual encoding was
sometimes used in STM if verbal rehearsal was prevented
o Wickens et al.…read more

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Long Term Memory
Description Key Study
Bahrick et al. (1975)
Duration Thirty seconds up to a life time
High school photograph study
Solomon Shereshevsky (Case study)
Capacity Unlimited
Famous mnemonist
Baddeley (1966)
Encoding Mainly semantic (meaning based)
Delayed recall study
Bahrick et al.…read more

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The Multi-store Model of Memory
The multi-store model of memory places emphasis on separate and sequential processes
Attention, coding and rehearsal are important processes
At each store, information may be lost through decay
Evidence for the Multi-store Model
1.…read more

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This suggested that the hippocampus may function as a memory gateway through which
new memories must pass before entering permanent storage
Evaluation of the Multi-store Model
Strengths Weaknesses
Short term memory may not be a single store. Evidence
from KF, a brain damaged patient; he showed STM ability
for visual information, but not verbal information.…read more

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The Working Memory Model…read more

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Evidence for the Working Memory Model
1.…read more

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This means it's harder to remember long words than short words as they can't fit onto the
But, the word length effect disappears if a person is given an articulatory suppression task,
such as saying `the the the' whilst reading the words
This repetitive task ties up the articulatory process and means you can't rehears the shorter
words more quickly than the long ones, evidencing the articulatory process
4. Baddeley et al.…read more

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Eyewitness Testimony
Eyewitness testimony is defined as the use of eyewitnesses to give evidence in court concerning the identity
of someone who has committed a crime.…read more

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Experiment Two ­ Post-Event Information
o To investigate whether memory is altered by post-event information which is incorrect in
relation to the scene witnessed
o Participants were allocated to three groups and asked to watch a traffic accident
o Group one were given the word "smashed"; group two were given "hit" and group three,
which acted as a control, were simply asked for the speed of the vehicles
o Group one produced higher speed estimates
o A week later, participants were recalled and…read more


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