Download aqa.cognitive.booklet

AS PSYCHOLOGY
Elizabeth Loftus
Cognitive
Psychology:
Memory
Name:
Tutor:
1
Cognitive Psychology: Memory
What is memory?
• The term memory can refer to the process in which we retain
information and knowledge. You may think that this is one process
but in fact it is split in to 3 basic processes.
• The first process is called Encoding. This is where a sensory
input (e.g. sounds or images) are transformed for it to be
registered in memory. Sound, vision and meaning are all encoded
differently.
• The second process is Storage. This simply is holding information
until it is required.
• The third stage is the process of Retrieval. This is where we
locate and use the information we have stored so we are
consciously aware of it.
Short Term Memory (STM) and Long Term Memory (LTM)
• Psychologists believe that Short Term Memory and Long Term
Memory differ in the amount of information that can be stored,
encoded and the duration the information can be held.
• Short Term Memory (STM) is a system for information that you
are currently thinking of. Information that is stored here is done
so only on a temporary basis.
• Encoding in STM: Psychologists believe that information in STM is
mainly encoded acoustically (sound).
• Capacity of STM: The capacity (how much of something can be
held) is limited in STM. Only a small amount of information can be
2
held. This can be demonstrated through studies using Serial Digit
Span techniques.
• Jacobs in (1887) investigated this. He read allowed a list of either
letters or numbers, with one syllable (‘w’ and ‘7’ were excluded).
The lists increased until participants could recall them only 50%
of the time. A wide age range was used in his sample. He found:
1. STM capacity for digits was 9, whereas letters was 7.
2. STM increased with age.
• The conclusion was that STM has a limited capacity of 5-9 digits
and age affects STM. This may be due to practice as we get
older. Numbers were easier to recall than letters.
• This is supported by Miller (1956) who coined the phrase ‘the
magic number seven plus or minus two’ (7+/- 2).
• Criticisms show that practice can affect information recall and
also newer research shows people have differing abilities
associated with their attention levels.
• Duration of STM: The duration of STM is short. It is less than 30
seconds.
• This is best described by Peterson and Peterson (1959) who used
nonsense trigrams (3 letters with no meaning, i.e. WQT). They had
to read these and then straight after had to count backwards in
3’s from a large number (e.g. 375). They counted for a specific
time period. The participants had specific times in which to recall
the trigrams ranging from 3 seconds to 18 seconds.
• The counting was done to stop the retention of the trigrams.
• The findings showed that 90% of trigrams were recalled after a 3
second interval and only 6% after an 18 second interval.
3
• Encoding in LTM: Most psychologists believe that information is
encoded semantically (meaning) in LTM. Baddeley (1966)
illustrated this in a study which involved lists of words. List A had
acoustically similar words (cat, mat, sad, sat). List B had
acoustically dissimilar words such as (pit, day, cow). List C had
semantically similar words such as (big, huge, tall). List D had
semantically dissimilar words such as (hot, safe, foul).
• After they were given the list they had a 20 minute retention
interval where they performed another task.
• This ensured that recall would have to come from LTM.
• The list C (semantically similar) was the least well remembered
(55%). This seems to suggest there was semantic confusion and
this leads to the idea that LTM information is encoded
semantically.
• The support for this comes from cognitive sense. In everyday life
we can remember the meaning of things but not the words. An
example would be a TV programme, you can remember what
happened (semantic) but not the exact words (acoustic).
• A criticism of this is that there are different types of LTM. One
of these is procedural memory. This includes things such as being
able to ride a bike or swim. They aren’t encoded in the same way
and are not generally studied. Remembering smells and songs can
also be included here.
4
• The potential capacity of LTM is unlimited. This is because we
know that our brains are not full of information on everything.
This is why there has been no limit placed on it.
• In LTM the duration lasts as long as you live. You will have
memories that you have from childhood that will last until you die.
Information in LTM doesn’t have to be rehearsed or repeated. For
example you may not have ridden a bike for many years but you
can still do it.
• Duration in LTM was demonstrated in a study by Bahrick et al
(1975). They gathered 400 participants aged 17-74 years and
asked them to remember names of classmates from high school
(free recall task). They were also shown a list of names and
photos. They had to identify their ex-schoolmates (recognition
task).
• Those who left school within the previous 15 years recalled 90%
of the names and faces in the recognition task. Those who had
left within the previous 48 years recalled 80% of names and 70%
of faces. These high percentages show we remember names and
faces for a very long time.
5
Table of differences between STM and LTM:
6
The Multistore Model
This activity will help you to:
• Describe the multistore model of memory
• Identifty the hypotheses of the multistore model
• Use evidence to assess the multistore model
• Evaluate the multistore model
The Multistore Model
Using the sources of information available to you, briefly describe the different components of the multistore model.
The Attention System
STM
The Short Term Store
The Rehearsal Loop
LTM
The Long Term Store
7
When we evaluate a psychological theory, we must take each of the claims it makes in turn, and establish whether they
are supported by the evidence we have from studies. Here are some of the claims made by the mutlistore model. For
each claim, explain whether the evidence supports of challenges it.
Claim
Evidence
Memory
consists of two
separate
storage areas
Glanzer & Cunitz (1966); Milner (1966)
Information is
moved from
STM to LTM by
rehearsal
Hyde & Jenkins (1973)
STM and LTM
are unitary
stores that
cannot be subdivided
Baddeley et al (1973); Tulving (1972)
Supported?
8
Working Memory model
Working Memory Baddeley and Hitch (1974)
 Baddeley and Hitch questioned the existence of a
single STM store. They felt that it was far more
complex than just a ‘stopping off’ point for
information to be transferred to LTM. They saw
STM as a system that actively worked on several
pieces of information at once. They weren’t
concerned with LTM.
 Groome (1999) compared WM to a computer
screen, where various operations are being
performed on current data.
 To replace the single STM store, Baddeley and
Hitch proposed a multi component memory system.
9
Diagram of WM
Components of WM:
Central Executive:
10
Articulatory control system:
Phonological store:
Visio-spatial scratchpad (or sketchpad):
11
Research support:
Gathercole and Baddeley (1993): Participants
followed a spot of light with a pointer (tracker
task). At the same time half the participants had
to describe the angles on a letter ‘F’. This group
found the task very hard as they were using the
visio-spatial scratchpad for both tasks. The other
group did a verbal task along with the tracker task
and had little difficulty performing both tasks.
Evaluation:
12
Eyewitness Testimony
Elizabeth Loftus
 You may be surprised how difficult it is to
remember what a 10p looks like without having one
in front of you.
 There will be a number of inaccuracies.
 We do not need to have 100% recall for all
information we use everyday. For example we only
need to know the shape of coins and notes to be
able to use them correctly.
Schemas:
 Knowledge packages built up through experience
of the world. They also help us to interpret new
experiences.
 For example-knowing that there will be tables and
chairs in a restaurant. This would be your
restaurant schema.
 They help to fill in gaps in knowledge we have.
 However they can lead to distortions when new
information doesn’t fit properly into our existing
knowledge.
 Cultural experiences and stereotypes affect
memory.
 These distortions are particularly interesting
when we look at EWT.
13
Research findings on the role of schemas:
 Brewer and Treyens (1981) looked at the effects
of schemas on visual memory. They asked 30 p’s,
one at a time, to wait in a room that had been set
up to look like an office for 35 seconds. In the
room there were objects such as a desk, chair,
calendar and typewriter.
 These objects were compatible with an office
schema.
 However there were a few items that were noncompatible, such as a skull, a pair of pliers and a
brick.
 In an unexpected recall task the following results
were found:
 P’s recalled the obvious office items that fitted
with schema expectancy, but were less successful
at recalling the strange items.
 8 p’s, however, recalled the really bizarre itemthe skull.
 Most errors in recall were substitutions. For
example p’s would add in items that weren’t there
such as pens, books, and a telephone, which would
have a high schema expectancy but weren’t there
on this occasion.
14
Task:
 Why do you think that some p’s recalled seeing a
skull in the office (Brewer and Treyens, 1981)?
 What implications does this finding have for the
schema theory?
EWT Stages:
 The witness encodes info into LTM (the event and
the person involved). May be partial as the event
occurs quickly, at night and accompanied by rapid,
violent, complex action.
 Witness retains info for a time. Memories may be
lost or modified during retention, other activities
may interfere with the memory itself.
 Witness retrieves memory from storage. What
happens next is there may be a presence or
absence of info that may affect the accuracy of
the memory.
Factors affecting EWT:
 The main factors affecting accuracy of memory
can be placed in to two categories:
 Witness factors: age, race, gender and individual
response to anxiety or stress.
 Event factors: duration of event and level of
violence witnessed.
15
 We will be looking at age, anxiety and the effect
of misleading information.
Anxiety and EWT:
A real crime or violence, usually imparts a feeling of anxiety or
stress on the witnesses.
The Yerkes-Dodson law (1908) suggests that up to a point, stress
improves performance but after that point, it has a bad effect on
performance. Deffenbacher (1983) proposed that the effect of
stress on EWT followed that law.
Optimum recall, past this point, recall declines.
Recall
Anxiety levels
Deffenbacher (1983) was one of the first to investigate links
between stress and EWT. He found that as we become moderately
stressed/anxious, performance in EWT improves. As we hit the peak
of stress our levels of accuracy drop because we feel fatigued.
A naturalistic study by Yuille & Cutshall (1986) studies witnesses to a
robbery where people had actually been killed or wounded. (What
steps would you want them to take if you were the ethics
committee?) They found that witnesses were very accurate despite
the extreme levels of stress. This has been supported by a study by
Christianson & Hubinette (1993) where victims of a bank robbery who
had been subjected to the most stress, were actually the most
accurate witnesses. Perhaps because their lives depended on it?
Research that supports this idea comes from Peters (1988). Tested
people visiting their local health centre. They visited the nurse, for
an injection, then spent time with a researcher. A week later they
were asked to describe the researcher and the nurse. It was found
16
that they remembered the researcher better than the nurse. This
was due to the fact their anxiety levels were heightened at the time
they were chatting to the researcher (after injection).
Deffenbacher (2004): reviewed his earlier approach and the claims it
was over simplistic.
He now believes that as stress increases, so does the accuracy of
the memory. When it hits the maximum there is a catastrophic
collapse, and accuracy is then severely lacking.
Task: Imagine you are a participant in a study where
you saw a bloodstained paper knife or a study where
you watch a violent film. Try to imagine how you might
feel during and after the investigation. Now, try to
answer the following questions:
1. What potential harm might participants suffer as
a result of being a participant in either study?
2. How might any risks to participants be reduced?
3. Give some reasons why you think it was ethical or
unethical to carry out these studies.
Age of witness:
 Age does seem to play a role in how much
information we can recall. Dent (1988) found that
children perform significantly worse than adults
when recalling details of events and also don’t do
as well when asked specific questions.
17
 However, if they are interested in a topic children
can recall just as well as adults do. (King and
Yuille, 1987).
 Children also appear to accept inaccurate
information from adults for fear of contradicting
adult authority figures.
 In a study specific to EWT Ochsner et al (1999)
asked children to watch a staged theft. They
found more accurate recall compared to children
who saw the staged event without the theft. In
this case it could be that the children
consolidated the memory of the theft by telling
others about it, or took the theft more seriously.
 Older people also have poor recall of events. Their
recall drops below that of young people and middle
aged people. They are more likely to make
mistakes and are poor at recalling specific details.
Elderly men in particular are more prone to
distortions through post-event misleading
information.
Evaluation:
 Research support: Cohen and Faulkner (1989)
showed p’s a film of a kidnapping and then
presented them with misleading details. It was
found that the older p’s (mean age 70) were a lot
more likely to than the younger p’s mean age 35)
to have been mislead by the suggestive
information.
18
 Loftus et al (1991) also found this when p’s were
shown a video tape of a crime the older p’s were
found to be more suggestible than the younger
adults who saw the tape.
 Conflicting evidence: Coxon and Valentine (1997)
found that when comparing the suggestibility of
children, young adults and elderly people after
watching a videotape of a crime, the elderly p’s
were worse at recall. However it was seen that
when they were tested for suggestibility they
were no worse than the young adults. In fact
they were seen to be less suggestible.
 Other conflicting evidence: It is still unclear why
these age effects occur. It could be that the
younger p’s have been more used to memory tests
recently. Or it could be that the older p’s poorer
health may be a factor in decline in memory. In
fact it may be this that is the important factor,
not age.
19
Loftus
Factors affecting eyewitness testimony:
• Elizabeth Loftus is a psychologist who argues that
eyewitness testimony in court is very unreliable.
• She looked at whether people reconstruct
memory, whether the memory persists (stays) or
whether they can be ‘led’ in to answering in a
certain way.
Leading Questions:
• Loftus and Palmer (1974): investigated how
information given after an event affects a
witness’s memory for that event.
• 45 participants took part. They all saw a video of a
traffic accident.
• After the video they were all asked the same
questions about the accident.
• Apart from 1 question which was about the speed
the cars were going.
• 9 participants had the cars ‘smashing’
• The other group had the verbs ‘hit’, ‘bumped’,
‘collided’, ‘contacted’.
20
• Results: Group with ‘smashing’ estimated the
highest speed of the cars.
• The participants were not very good at estimating
how fast the cars were actually travelling.
• Speed estimates depended on the verb used.
Table of results:
Verb
Smashed
Collided
Bumped
Hit
Contacted
Mean Speed Estimates
Conclusion:
• We can conclude that people’s memory for an
event can be influenced by the questions they are
asked about it and those questions can distort
(change) our long term memory for an event.
• We don’t know whether the reported speed was
due to a genuine change in the participant’s
memory, or through demand characteristics
(participants guessing the true nature of the
experiment). (Gross, 2003).
21
Evaluation:
• A similar follow up study was done where
participants were given a question about
whether they had seen broken glass on the
road (there was none). 14% of participants
with ‘hit’ reported seeing glass. Whereas 32%
of the participants with the word ‘smashed’
reported seeing glass. There seems to be
evidence that suggests post event misleading
questions can have an adverse effect on
EWT.
Eyewitness Testimony task:
1. What are the 3 stages that eyewitness testimony
goes through?
2. What was the general assumption about EWT
before the Devlin report?
3. In your own words write down the APFCC of
Loftus & Palmer (1974).
4. Which factors effect EWT?
5. What does research suggest about the reliability
of EWT?
6. Do leading questions effect EWT?
22
7. Do people believe EWT?
Which of these items are true and which are false?
Loftus & Palmer (1974)
1 used a repeated measures design with 45 students
2 short film clips of traffic accidents were shown
3 L & P found that the speed estimates from pps
varied with the verb used in the question
4 the population validity of this study was
questionable as they only used students
5 the mundane reality of this study was good as pps
were less anxious than if seeing a real accident
6 subsequent studies offered a monetary reward for
the correct answer, eliminating design effects
7 the conclusion of this study was that misleading
information alters memory recall
T or F
T or F
T or F
T or F
T or F
T or F
T or F
23
Read the following passage at normal reading speed
once. Then turn the page over and write down as many
points from the passage as you can remember.
24
ACTIVITY: Out of context
Look at the following picture. Then turn the page over
and write down/draw as many points from the picture
as you can remember
25
STUDY THIS PICTURE
26
27
The Cognitive Interview: CI
What is the cognitive interview?
• So far we have gone over what the problems are
with eye witness testimony.
• Here however we will look at the cognitive
interview a technique used by the police in order
to gain more accurate information.
Fisher and Geiselman (1992):
• They believed that one way in which we remember
events more accurately is to put them in to
context.
• They also said that we can remember more if we
are given retrieval cues.
Four components of the original cognitive interview:
1. Report everything: the interviewer encourages the
reporting of every single detail of the event, even
though it may seem irrelevant.
2. Mental reinstatement of original context: the
interviewer
encourages
the
interviewee
to
mentally recreate the environment and contacts
from the original incident.
28
3. Changing the order: the interviewer may try
alternative ways through the timeline of the
incident by reversing the order in which events
occurred.
4. Changing the perspective: the interviewee is asked
to recall the incident from multiple perspectives,
for example by imagining how it would have
appeared to other witnesses present at the time.
• The assumption of the first 2 components is to
see if there is a consistency between the actual
incident and the recreated incident.
• The other 2 components are there to see if the
information observed can be retrieved from
memory via other ‘routes’.
Research into the cognitive interview:
• A meta-analysis (collection of data from lots of
different studies) of 53 studies found, on
average, an increase in the amount of correct
information generated in the CI compared with
standard interviewing techniques (Kohnken et
al.,1999).
29
• However most of these studies were tested in the
lab and witnesses were usually college students.
• Milne and Bull (2002) examined the relative
effectiveness of each component.
• Undergraduate s and children were interviewed
using one component and compared to a control
group (who were instructed simply to ‘try again’).
• Recall across all components was similar and not
much different than the control group.
• However
when
the
components
were
used
together the recall was much higher.
Evaluation:
• The problem with evaluating the CI is that it no
longer has one procedure. It is a collection of
related techniques.
• Thames Valley Police use the basic Fisher and
Geiselman
technique
without
the
‘changing
perspectives’ component.
• Other police forces who say they use the
technique only use the ‘reinstate context’ and
‘report
everything’
components
(Kebbell
and
Wagstaff, 1996).
30
• An enhanced version of the technique by Fisher
and Geiselman (1992) requires more training and
requires more strain on the interviewer.
• Memon et al. (1994) showed that experienced
detectives received only a brief (4 hours) training
in the use of CI, which did not produce any
significant
increases
in
in
the
amount
of
information gained from the witnesses about an
incident
(when
compared
with
standard
techniques).
Improving Memory:
31
 Strategies for memory improvement: Organisation
 Demonstrations show that organised material is
easier to recall than disorganised material.
 Evidence suggests that when given random
material, we try to organise it.
 Demonstrations that instructions to organise
material enhance participants recall.
 There are many studies which show the
importance
of
organisation
for
memory
improvement.
 Many of these involve mnemonics, which are
strategies for memory improvement.
 Simply using a list to remember your shopping
would count as a simple yet effective mnemonic
device.
Categories task:
 In a moment you will be shown 2 lists of words for
20 seconds
 You will be shown each list one at a time.
 After the first list is shown to you I want you to
write down as many of the words as you can.
 I will then show you the other list and then you
will do the same task, writing down as many words
as you remember.
32
Chunking:
 Our STM capacity can be improved if separate
‘bits’ of info are grouped in to larger ‘chunks’.
 For example 19391945 can be chunked in way that
it will be seen as the start and end date of the
Second World War.
 When we read we ‘chunk’ letters in to words and
words in to sentences.
 Miller preferred to view STM as 7+/-2 chunks of
information rather than individual pieces of
information.
Imagery:
 Imagery is seen to be the most important
mnemonic (Rolls, 2007).
 The method of loci is used here.
 This is the oldest documented mnemonic.
 Loci means locations
 It basically refers to the individual making mental
representations of familiar routes i.e. your walk to
college.
 You then use images to represent the words or
items you are trying to remember.
 Then you visualise the route and place the images
at ‘loci’ along the route.
 The more bizarre the image the better.
 To recall the list you recreate the route in your
head, noticing the various items from the list
33
along the way, until you have remembered the
entire list.
Evaluation of Imagery:
 An advantage of this method is that you recall
information in the correct sequence.
 However you cannot re-use the route too often
because you might cause interference with other
information you might be using.
 It is difficult to remember a certain item because
you have to go through the entire list.
Peg word mnemonic:
 The word mnemonic just means a way to improve
memory.
 The mnemonic below uses visual imagery and
rhyme and rhythm, it also uses numbers instead of
places. The numbers are transformed in to images
by using a simple rhyme.
 One is a bun
 Two is a shoe
 Three is a tree
 Four is a door
 Five is a hive.
 For this to work well you have to imagine the
number interacting with the item you have rhymed
the number with.
34
 Evaluation:
 You have to learn the rhyme by rote (repetition)
so there is more to remember here.
 One major problem is that when there is more
than one list to be recalled then there can be
interference between the lists.
 This makes it a slow process. Coupled with the
fact you have to repeat the rhyme each time.
 It also doesn’t work well with abstract words like
‘hope’. You also need to practice the technique
extensively.
 ‘Non-memory’ factors that improve memory
 Hermann and Palmisano (1992) state that a
person’s environment or their emotional state can
have an effect on the ability to remember
information.
 Context remembering/forgetting links in with the
ideas mentioned above. A study by Godden and
Baddeley (1975) got underwater divers to learn
lists of words either on dry land or underwater. If
they were asked to recall the words in the same
place they were learnt, i.e. underwater, they
recalled more words than if they were in a
different place for example on dry land.
State-dependent remembering/forgetting:
 This looks at a person’s emotional state and also
the physical state they are in. For example
Goodwin et al (1969) looked at alcohol. They found
that when a participant was drunk and hid money
35
they were more likely to find the hiding place
when they were in their original drunken state.
ASSESSMENT:
1. Define what is meant by the terms ‘encoding’, ‘capacity’ and
‘duration’. (2 + 2 + 2 marks)
2. Distinguish ONE difference between STM and LTM as
suggested by the MSM. (3 marks)
3. Describe the multi-store model of memory. (6 marks)
4. Explain one strength of the MSM. (2 marks)
36
_______________________________________________
_______________________________________________
_______________________________________________
5. Outline TWO weaknesses of the MSM. (2 + 2 marks)
6. Using the MSM, outline the processes involved in storing and
retrieving material in LTM. (4 marks)
7. Explain how evidence from brain damage patients has helped
to support the multi-store model. (6 marks)
37
_______________________________________________
_______________________________________________
8. ‘Peter was trying to remember the name of his first teacher
at primary school without success. Then his mother managed
to find an old class photo, which she showed Peter. The name
of his teacher then popped into his mind.’ Explain why Peter
was suddenly able to remember. (6 marks)
38
9. Outline and evaluate the MSM. (12 marks)
39
______________________________________________
10 Explain your answer.
40
41
Model answer: 12 mark essay question.
OUTLINE AND EVALUATE THE MULTI-STORE MODEL OF MEMORY (12 MARKS)
The multi-store model (MSM) of memory was proposed by Atkinson and Shiffrin
(68). It suggests that our memory is divided into 3 memory stores: Sensory
memory, Short term memory (STM) and Long term memory (LTM). Information
flows firstly through the sensory memory to STM using attention, it can then be
transferred to LTM using elaborative rehearsal but goes back to STM using
retrieval.
The sensory memory is a store which processes information for a very short
moment in time (Sperling ’60) based upon our 5 senses which decays quickly.
The capacity of STM is 7 +/- 2 according to Miller (56) who discovered this using
a digit span technique. The duration of STM is 18 seconds according to Peterson
and Peterson (59) who developed the Brown-Peterson technique which uses trigrams
and interference tasks to assess memory, however, according to Atkinson and
Shiffrin (68) the duration is 30 seconds because it can be extended to this length
with rehearsal. In terms of encoding it is acoustic according to Baddeley (66)
following an experiment using confusing words which either sounded similar or had
the same meaning.
According to Solso (91) the capacity of our LTM is potentially enormous even in
comparison to a computer. The duration of LTM is according to Bahrick et al (75)
a minimum of 34 years however it probably a great deal longer from his study into
High School Yearbook photos. The encoding of LTM is believed to be semantic
according to Tulving (89).
One strength of this model is the amount of supporting research, for example Murdock
suggested that the MSM could account for the primacy and recency effects seen by
Glanzer and Cunitz (66), and thus suggests that the model is reliable.
However, in criticism, the experiments used to suggest capacity, duration and encoding
limits lack ecological validity because they were conducted in laboratories which are
artificial settings and may produce demand characteristics in the participants.
An additional criticism is that the model is to simplistic, according to Shallice and
Warrington (70) who conducted an investigation into KF. He was a patient who suffered
from brain damage meaning he was unable to process verbal information in the STM but
could process visual information thus suggesting STM is not a single store. This idea is
supported by Baddeley and Hitch (74) with their working memory model.
An additional strength of the MSM is provided by Scoville and Milner (57), they
suggested that the hippocampus is the gateway to the LTM store from their study of an
epileptic patient called HM. HM’s hippocampus was removed in order to ease his epilepsy
resulting in him being unable to form new long term memories, though he could access
old long term memories he had already made. Therefore, suggesting that memory is
comprised of more than one store and thus the MSM is an accurate description of
memory.
In conclusion, there are numerous strengths and weaknesses of the MSM however,
more up to date research needs to be conducted in order to fully assess it’s reliability
and validity given changes in technology.
42
Model answers
Memory Question
Booklet
1) Explain how the duration of STM has been investigated (5)
Peterson and Peterson (1959) investigated the duration of STM in a lab
experiment using the Brown-Peterson technique. They showed ps trigrams
(eg BLM) one at a time and then asked them to count backwards in 3s
from a given number. This was done in order to prevent rehearsal of the
trigrams, which would have biased the experiment. The time delay
between presentation and recall of the trigrams was varied between 3
and 18 seconds. Ps were then asked to recall the trigram. The trigrams
contained no vowels so as to avoid the influence of LTM.
Other psychologists have investigated the duration of STM in a similar
way but have used only a small number of trigrams in order to prevent
confusion.
2) Explain how studies of STM have been controlled (4)
Peterson and Peterson controlled their study into short term memory by
ensuring there were no vowels in the trigrams, meaning that ps could not
make words from them. They also prevented ps from rehearsing using an
interference task. In studies using word lists, the researcher ensures
that the words in each list are of equal difficulty and length etc.
Researchers control the rate of presentation of their stimuli, ensuring
that all words/digits are presented at the same speed.
3) Explain what research into STM has shown (6)
STM research has shown that STM has a short duration. Peterson and
Peterson (1959) found that ps forgot trigrams very rapidly when they
could not rehearse them. After 18 seconds, only 10% of trigrams were
recalled.
Miller showed that the capacity of STM is 7+/-2, meaning that most
people can hold about 7 groups of meaningful information in their
memories at once – some a few more, others a few less.
43
Baddeley found that in an STM task, ps confused words that sounded
alike but could remember the same number of words that did not sound
alike. This shows that STM encodes acoustically.
(Shulman found that STM can encode semantically)
4a) Sally is a telephone executive. She can recall landline numbers while
she dials but if she calls a mobile she cannot remember the number.
Explain why this may be. (3)
This may be because the capacity of STM is very small – around 5-9
digits. A landline number is shorter than a mobile phone number and so is
more likely to be remembered. Sally can clearly not fit the 9 digits of a
mobile number into STM.
OR – Perhaps Sally can remember a landline number because she forms a
chunk with the area code, which she already knows. Then she only has to
recall 1 chunk + 6 digits – this is within the capacity of STM.
4b) Sally has noticed that even though she remembers landline numbers
while she dials, by the end of the call, she has forgotten them. Explain
why this may be. (3)
It is likely that Sally has forgotten the numbers by the end of the call
because of the short duration of her STM. Research has shown that STM
duration is only 18 seconds if there is no rehearsal. When she is talking
on the phone she cannot rehearse and so the number is forgotten.
Explain how the duration of LTM has been researched by psychologists
(6)
Shepard researched the duration of LTM by showing ps pictures and
recording how many they could recall 4 months later.
In a lab experiment, Bahrick et al researched LTM using a high school
year book. He took ps aged 17-74 and asked them to free-recall their
class mates from high school (ie recall their names off the top of their
head). Next, he tested recognition memory by asking them to recognise
names of classmates from a list of names and to recognise pictures of
classmates. He recorded the number of classmates recalled and compared
44
it to the age of the participant in order to determine the duration of the
memory.
45