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Capacity in short term
Memory. (STM).
Key study: The digit span · Findings:
technique Jacobs (1887) · Participants recalled on average 9 numbers (digits)/
Aim: To investigate the capacity of letters.
STM · Conclusion
· Short term memory has a limited capacity of 5-9
Miller (1956) found that we can hold items. Letters may be difficult to remember.
5-9 items in our short term memory.
Another way to say this is · Evaluation
7+/-2 · The research was artificial and not like what we would
do in real life (Lacks ecological validity) meaningful
information be recalled better which increases the
capacity of the short term memory.
Participants took part in a Lab experiment where they
were read a list of numbers of letters at a rate of 1 per
second (a digit span). After each row, participants were
asked to repeat the list back to the experimenter in the
same order. With each correct answer, the length of the
list was gradually increased until the participants could
not recall the sequence correctly.…read more

Slide 2

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Duration in STM.
Key Study: Aim: to investigate the duration of short term memory.
Nonsense trigrams (Peterson
and Peterson 1959) Procedure: 24 undergraduates took part in the study which
was a lab experiment. Participants were read out sets of 3
letters with no meaning e.g. LJK these are called nonsense
Conclusion: trigrams.
When rehearsal is prevented short
term memory has a very short
Immediately after each trigram was read out, the participant
duration of less than 18 seconds.
had to count backwards in 3's starting from a large 3 digit
Evaluation: number for a specified period of time (the retention interval
Only a small sample was taken and period). This period of time increased gradually from each
only consisted of undergraduate trigram read out to the participant (from 3-18 seconds). Once
students, so they were not testing a the time was up, participants had to recall the letters of the
large sample of ages so the results trigram in the correct order.
are unreliable.
It is not true to life so it lacks Findings: Participants could remember approximately 90% of
ecological validity and the results the trigrams after a 3 second retention interval which dropped
cannot be generalise the results to to 20%after 9 seconds and 2% when there was an 18 second
situations outside the lab. interval.…read more

Slide 3

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The multi-store model of
Key Study: Atkinson and Schiffrin
Characteristics of the multi store
- Structural model
- information is passed from store
to store in a linear way (ONE
- Short term and long term are
unitary stores (not sub divided into
smaller components)
- Information has to be paid
attention to in order for it to
progress into the short term
- Rehearsal is need at all points in
order to prevent the information
being forgotten…read more

Slide 4

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Evaluation of the MSM.
Strengths of the MSM: Research support for the MSM:
- Simple model to understand - Evidence from brain scans show that different areas of
- The model is influential as it has the brain are used for different tasks.
generated a lot of research into - Nonsense trigrams showed that rehearsal is important for
memory. information to remain in the STM and to be transferred to
- The model is supported by studies LTM when rehearsal is prevented duration is very short.
of amnesiacs such as the case This supports MSM as the model suggests that rehearsal
study of HM must occur for information to transfer from STM to LTM.
- Case study of HM Milner et al (1978) shows that the
rehearsal loop must be functioning correctly to maintain
Weaknesses of the MSM: STM, otherwise they are forgotten. This supports the MSM
- The model is oversimplified, in as being a linear and unitary system, it suggests that LTM'
particular when it suggests that s cannot form if rehearsal is not successful within the STM.
both short-term and long-term
memory each operate in a single, Research contradicting the MSM
uniform fashion. - Case study of KF ­ Shallice and Warrington (1974)
- The model suggests rehearsal suggests that information can bypass the STM and be
helps to transfer information into transferred into LTM. This contradicts the MSM as the
LTM but this is not essential MSM would suggest that this is not possible as rehearsal
- However, the models main must occur fully in STM for LTM's to form (linear System)
emphasis was on structure and
tends to neglect the process
elements of memory (e.g. it only
focuses on attention and
rehearsal).…read more

Slide 5

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The working memory model.
Central Executive: Phonological loop: has two sub ­ systems
- Has overall control
- Pays direct attention to tasks Phonological store:
deciding what will enter from
- Stores verbal information (words heard or seen) in a
our senses or be received from
speech based from
our LTM
- Information is only held for a short time (1.5-2 seconds)
- It has a limited capacity
- Receives information directly from LTM or our senses
Visuo ­ spatial Sketchpad Articulatory control process
- Holds visual information (what - Where verbal information stored in the phonological store
things look like) and spatial is rehearsed so it is not lost
information (where it is in the
visual field) for a short period of
- Has a limited capacity…read more

Slide 6

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The Working Memory Model.
Key study: Weaknesses:
Baddeley and Hitch (1974) - Lieberman criticizes the working memory model as the Visuo-
spatial sketchpad (VSS) implies that all spatial information was
first visual (they are linked).
- There is little direct evidence for how the central executive
Strengths: works and what it does. The capacity of the central executive
-The working memory model has never been measured.
explains a lot more than the multi- - Working memory only involves STM so it is not a
store model. comprehensive model of memory (as it does not include SM or
-It makes sense of a range of tasks - The working memory model does not explain changes in
- verbal reasoning, comprehension, processing ability that occur as the result of practice or time.
reading, problem solving and visual
and spatial processing. - They proposed the working memory model which offers a
-The model is supported by more complex explanation of short term memory tan the multi-
considerable experimental store model of memory.
evidence - They suggested that the short term memory is more complex
than just a stopping station between our sensory memory and
our long term memory.
- They devised the dual task technique to test the idea that
there is more than one component in short term memory.
- The working memory helps us keep track of what we are doing
and holds information long enough for us to make decisions
about it.…read more

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