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Psychology Kf Case Study

Examine one interaction between cognition and physiology in terms of behaviour

A quick introduction to models of memory

Uncovering the assumptions of the Multi-Store Model

The MSM was a hugely important model of memory. It is worth stressing some of the key assumptions of the model (in order to help you to address the command term of 'examine'). These assumptions include:
  • That memory is a serial process, with a transfer of information happening in a set series (from SM to STM to LTM)
  • Each type of memory has a separate store (so for example STM uses a different part of the brain than LTM)
  • That there is a single, unitary store for each type of memory (there is just one specialised area for STM, for example)

Study 1 - Scoville and Milner (1957) - Case study of H.M.

Which study to choose?

One difficulty which can arise in talking about H.M. is simply the fact that because there is SO much research about him, it can be confusing knowing which study to choose. For your purposes there are two main studies which cover most of the major findings:
  • Scoville, W.B. and Milner, B. 1957. Loss of recent memory after bilateral hippocampal lesions. J Neurol Neurosurg Psychiatry. 20(1):11-21. This was the original H.M. study where the surgery was described, along with H.M.'s memory deficits.
  • Corkin et al (1997) H. M.'s medial temporal lobe lesion: findings from magnetic resonance imaging. J Neurosci. 17(10):3964-79. This was the first study to use MRI to look at the damage to H.M.'s brain, giving us a much clearer picture of the exact areas which had been damaged (although not as clear as the post-mortem video below)

Assignment 2  - Applying the case of H.M. to the command word

Look back at the assumptions of the Multi-Store Model of Memory above. What can H.M.'s case tell us about these assumptions? Are they all accurate? Which ones does the case support? Which ones does the case criticise? There is a lot that you can potentially say here, so think carefully about it! Write at least half a page of analysis.

A corresponding case - Clive Wearing (Sachs, 2007)

Study 2 - Shallice and Warrington (1970) - Case Study of K.F.

Finding DOUBLE DISSOCIATIONS in cases of brain damage

22 mark section B question

Physiology is the internal, biological mechanisms of living organisms – the way the organism functions 

Cognition is the mental process of acquiring and processing knowledge and understanding through thought, experience and the senses. Cognitive processes include perception, attention, language, memory and thinking. 

Focus on command term - examine

Consider an argument or concept in a way that uncovers the assumptions and interrelationships of the issue

Level 3

The command term 'examine' requires you to carefully analyse arguments and evidence to show how and why they explain an aspect of behaviour. This could be finding similarities and differences between theories, or assessing whether conventional ideas and theories are supported by evidence
Here we will be looking at memory, and assessing the assumptions behind memory and the interrelationships of a number of famous case studies of brain damage.


Memory is defined as the cognitive process whereby information is encoded, stored and retrieved. Memory is clearly a crucial part of what it is to be human - imagine trying to live life without it - and it has been extensively studied by psychologists. 

One of the very influential early models of how our memory works was the Multi-Store Model of Memory (Atkinson and Shiffrin, 1968). Read this page on the Simply Psychology site for a good introduction to the model. 


The Multi-Store Model of Memory

H.M. is undoubtedly the most famous man in the history of Psychology... but he never knew it. Following an operation to cure him of epilepsy, H.M. (real name Henry Molaison), awoke with the total inability to create any new memories. Tragic as it was for Henry the man, the subsequent fifty years of study provided fascinating insights into the complex nature of memory and the brain (the fact that he never remembered having taken tests before meant he never got bored, so he was in many ways a dream test subject)!

There are huge numbers of excellent summaries of H.M.'s life and contribution to psychology, but this Psychology Today article is a decent place to start. A more detailed summary of the numerous studies involving H.M. over his lifetime and the conclusions that can be drawn from them can be read in this article.

Anterograde and Retrograde amnesia

Two important terms when discussing memory loss are anterograde and retrograde amnesia. Retrograde amnesia means forgetting events that we have already committed to memory (forgetting things from our past). In contrast, anterograde amnesia is the inability to form any new memories.

This page on intropsych.com contains a nice example to help clarify the difference between the two.

Assignment 1 - HM case summary

Use any internet resources that you can find to produce a detailed summary of H.M. case study. Make sure you answer the following questions:
  • What damage was done?
  • What methods were used to investigate him?
  • What conclusions were drawn about human memory from H.M.'s case? 

H.M.'s post-mortem MRI scan

This video shows the results of an MRI scan taken on the night that H.M. died. Because he wasn't moving (obviously) they were able to scan for nine hours in astonishing detail. Suzanne Corkin, who performed the scan, noted

Many structures are extremely clear:

You can see the dura mater (the thick membrane that covers the brain), blood vessel walls, his lesions (black holes), and the residual tissue near the lesions. The ventricles (spaces in the brain that contain cerebral spinal fluid) are huge, the cerebral cortex is atrophied, and the corpus callosum (bundles of white matter that connect the left and right sides of the brain) is thin. In the back of Henry’s brain, you see a shriveled cerebellum, which is a side effect of taking an anti-seizure medication, Dilantin, in high doses for decades.


As  you watch the video, try to identify all of these observations for yourself.

Slicing H.M.'s brain

Clive Wearing's mind-blowing diary
Clive Wearing is a case which corroborates the findings of the H.M. case study. A musician who suffered damage to his hippocampus (like H.M.), though through a different means (a viral infection rather than an operation), he suffered many of the same sorts of deficits as H.M. More information can be read and watched here, and here is a radio show on him.

HOWEVER, again (like with H.M.) the conclusions to be reached from the case are not as simple as you might at first imagine. Think carefully about how the details fit with the assumptions of the Multi-Store Model.


KF suffered brain damage as a result of a motorcycle accident. KF had no problem with long-term memory, but his digit span was only two items (in others words he could only remember two digits at a time whereas, on average, people remember seven digits in short-term memory).  These findings suggest that different parts of the brain are involved in short-term and long-term memory. Warrington & Shallice found that KF’s short-term forgetting of auditory letters and digits (things that are heard) was much greater than his forgetting of visual stimuli.  They also found that KF’s short-term memory deficit was limited to verbal materials (e.g. letters, words) and did not extend to meaningful sounds (e.g. cats mewing), in other words he couldn't remember things like words, but could remember meaningful sounds. 

Assignment 3 - Analysing K.F

Looking at the case summary on the left, what conclusions can you draw in relation to the Multi-Store Model? Find as many points as you can.
Here is the full research paper from Shallice and Warrington (1970). Use it to find greater insights into the case of K.F., and to analyse the conclusions of the researchers.

Evaluating research methods

All of these three studies are case studies. This clearly has major implications for how widely we can confidently generalise the findings from them.

Assignment 4 - Evaluating case studies

Create a table of the pros and cons of case studies. Make sure that for each point you are able to relate it to each specific case study.

Analysing the interrelationships in case studies of memory

The other requirement of the command term is to 'analyse the interrelationships of the issue'. 

What relationships can you see between the three studies above?

Refer back to the assumptions of the Multi-Store Model. Are there any new insights that you can gain through looking at all of the results holistically? 

See below for one suggestion...
In the case of H.M. and K.F., they form a double dissociation between short-term and long-term memory stores. 
What conclusions can we draw from this fact?
HM and KF have damage in different areas...
A double dissociation is a term given to a situation where cognitive abilities which are related are found to be located in different areas of the brain. We can confirm this by finding a patient who can do one skill but not another, and then finding another patient with the opposite problem. See the picture below for clarification. 













A double dissociation is very strong evidence that the two skills are controlled by separate brain areas


Triangulating evidence

The cases of Clive Wearing and H.M. both involve damage to the hippocampus, an area that we already have seen is hugely important for learning and memory (e.g. in the Hormones and Environment on Physiology pages). These studies can therefore be used as triangulating evidence which reinforce the importance of the hippocampus in long term memory.

H.M. in his role as the most studied man in history, had his brain scanned numerous times. This information can be used in the 'Brain Imaging Technologies' section. 

Assignment 5 - Section A question

Read back through the details of the studies above, and then answer the following question from memory:

Analyse the interaction between cognition and memory (8)
All sections with a Level 3 command term can be assessed in a 22 mark essay (remember that a learning objective with a 22 mark command term could also come up as an 8 mark question, but not vice versa). 
Although any Level 3 command term could be asked, we'll concentrate on the one given in the learning objective, so the question is

Examine one interaction between cognition and physiology in terms of behaviour (22)

You will need to plan an essay which will be about 2-3 sides of A4 long, including a detailed focus on the command term.

The marking criteria are below. ALWAYS refer to these before you begin to plan your essay. It is crucial that you know what the examiners are looking for so that you can write exactly what is needed for top marks!

Planning a great 22 mark question

KNOW THE COMMAND TERM! This is absolutely crucial! A different command term requires a different style of essay, so you need to tailor what you write to the question. You will still be able to use the same pieces of information, but how you use them may vary.

PLAN PLAN PLAN! Every year the examiners' comments mention that essays which are clearly planned score the best marks. FOLLOW THEIR ADVICE! Don't be afraid to spend up to 10 minutes in an exam planning your essay (and longer earlier in the year when are learning and practising). 

USE EVIDENCE! You have 2 detailed studies here to use, but you should also look to find triangulating evidence using other experimental methods or from other areas of the syllabus 

EVALUATE! You must evaluate the studies you present. Evaluating means talking about the strengths and weaknesses of the study as well as the strengths and weaknesses of the level of analysis as a whole with reference to the question (e.g. reductionist explanation of genetics in some behaviour) 

Revision

Extension

Scoville and Milner (1957) actually reported on a number of case studies in their famous paper. You can read them below, as well as their initial report on H.M.
scoville_milner_1957.pdf
File Size: 376 kb
File Type: pdf
Download File


We will look at some of the details from the video below in the next section, but it is also relevant to what we have covered here.

Memory Revision Notes


The Multi-Store Model

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The multistore model of memory was proposed by Atkinson and Shiffrin and is a structural model. They proposed that memory consisted of three stores: sensory register, short-term memory (STM) and long-term memory (LTM). Information passes from store to store in a linear way. Both STM and LTM are unitary stores.

Sensory memory is the information you get from your sense, your eyes and ears. When attention is paid to something in the environment it is then converted to short-term memory.

If any information is not important then it decays or disappears. Once in the short term memory informed can be rehearsed and some information is rehearsed and then passed into long term memory.

Each store has its own characteristics in terms of encoding, capacity and duration.

  • Encoding is the way information is changed so that it can be stored in the memory. There are three main ways in which information can be encoded (changed): 1. visual (picture), 2. acoustic (sound), 3. semantic (meaning).

  • Capacity concerns how much information can be stored.

  • Duration refers to the period of time information can last in the memory stores.

Sensory Register

    • Duration: ¼ to ½ second

    • Capacity: all sensory experience (v. larger capacity)

    • Encoding: sense specific (e.g. different stores for each sense)

Short Term Memory

    • Duration: 0-18 seconds

    • Capacity: 7 +/- 2 items

    • Encoding: mainly acoustic

Long Term Memory

    • Duration: Unlimited

    • Capacity: Unlimited

    • Encoding: Mainly semantic (but can be visual and acoustic)

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One strength of the multistore model is that is gives us a good understanding of the structure and process of the STM. This is good because this allows researchers to expand on this model. This means researchers can do experiments to improve on this model and make it more valid and they can prove what the stores actually do.

It has now become apparent that both short-term and long-term memory are more complicated that previously thought. For example, the Working Model of Memory proposed by Baddeley and Hitch (1974) showed that short term memory is more than just one simple unitary store and comprises different components (e.g. central executive, Visuospatial etc.).

The model suggests rehearsal helps to transfer information into LTM but this is not essential. Why are we able to recall information which we did not rehearse (e.g. swimming) yet unable to recall information which we have rehearsed (e.g. reading your notes while revising). Therefore, the role of rehearsal as a means of transferring from STM to LTM is much less important than Atkinson and Shiffrin (1968) claimed in their model.

Research Study for both STM & LTM

AO1 or AO3

Research studies can either be knowledge or evaluation:

  • If you refer to the procedures and findings of a study, this shows knowledge and understanding.
  • If you comment on what the studies shows, and what it supports and challenges about the theory in question, this shows evaluation.

Glanzer and Cunitz showed that when participants are presented with a list of words, they tend to remember the first few and last few words and are more likely to forget those in the middle of the list, i.e. the serial position effect.

This supports the existence of separate LTM and STM stores because they observed a primacy and recency effect.

Words early on in the list were put into long term memory (primacy effect) because the person has time to rehearse the word, and words from the end went into short term memory (recency effect).

Other compelling evidence to support this distinction between STM and LTM is the case of KF (Shallice & Warrington, 197) who had been in a motorcycle crash where he had sustained brain damage. His LTM seemed to be unaffected but he was only able to recall the last bit of information he had heard in his STM.


Types of Long Term Memory

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One of the earliest and most influential distinctions of long term memory was proposed by Tulving (1972).  He proposed a distinction between episodic, semantic and procedural memory.

  • Procedural memory is a part of the long-term memory is responsible for knowing how to do things, i.e. memory of motor skills.  It does not involve conscious (i.e. it’s unconscious - automatic) thought and is not declarative.  For example, procedural memory would involve knowledge of how to ride a bicycle.

  • Semantic memory is a part of the long-term memory responsible for storing information about the world.  This includes knowledge about the meaning of words, as well as general knowledge. For example, London is the capital of England. It involves conscious thought and is declarative.

  • Episodic memory is a part of the long-term memory responsible for storing information about events (i.e. episodes) that we have experienced in our lives.  It involves conscious thought and is declarative.  An example would be a memory of our 1st day at school.

Cohen and Squire (1980) drew a distinction between declarative knowledge and procedural knowledge.  Procedural knowledge involves “knowing how” to do things. It included skills, such as “knowing how” to playing the piano, ride a bike; tie your shoes and other motor skills.  It does not involve conscious thought (i.e. it’s unconscious - automatic) .  For example, we brush our teeth with little or no awareness of the skills involved.

Whereas, declarative knowledge involves “knowing that”, for example London is the capital of England, zebras are animals, your mums birthday etc.  Recalling information from declarative memory involves some degree of conscious effort – information is consciously brought to mind and “declared”.

The knowledge that we hold in semantic and episodic memories focuses on “knowing that” something is the case (i.e. declarative).  For example, we might have a semantic memory for knowing that Paris is the capital of France, and we might have an episodic memory for knowing that we caught the bus to college today.

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Evidence for the distinction between declarative and procedural memory has come from research on patients with amnesia. Typically, amnesic patients have great difficulty in retaining episodic and semantic information following the onset of amnesia.

Their memory for events and knowledge acquired before the onset of the condition tends to remain intact, but they can’t store new episodic or semantic memories. In other words, it appears that their ability to retain declarative information is impaired.

However, their procedural memory appears to be largely unaffected. They can recall skills they have already learned (e.g. riding a bike) and acquire new skills (e.g. learning to drive).


Working Memory Model

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The working memory model (Baddeley and Hitch, 1974) replaced the idea of a unitary STM. It suggests a system involving active processing and short-term storage of information.

Key features include the central executive, the phonological loop, and the visuospatial sketchpad.

The central executive has a supervisory function and acts as a filter, determining which information is attended to. It can process information in all sensory forms, directs information to other slave systems and collects responses. It has limited a limited capacity and deals with only one piece of information at a time.

One of the slave systems is the phonological loop which is temporary storage system for holding auditory information in a speech based form. It has two parts: (1) the phonological store (inner ear), which stores words you hear; and (2) the articulatory process (inner voice), which allows maintenance rehearsal (repeating sounds or words to keep them in working memory while they are needed). The phonological loop plays a key role in the development of reading.

The second slave system is the Visuospatial sketchpad (VSS). The VSS is a temporary memory system for holding visual and spatial information. It has two parts: (1) the visual cache (which store visual data about form and colour), and (2) the inner scribe (which records the arrangement of objects in the visual field, and rehearses and transfers information in the visual cache to the central executive).

The third slave system is the episodic buffer which acts as a 'backup' (temporary) store for information which communicates with both long term memory and the slave system components of working memory.

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Working memory is supported by dual task studies. It is easier to do two tasks at the same time if they use different processing systems (verbal and visual) than if they use the same slave system.

For example, participants would find it hard to do two visual tasks at the same time because they would be competing for the same limited resources of the visuospatial sketchpad. However, a visual task and a verbal task would use different components and so could be performed with minimum errors.

The KF Case Study supports the Working Memory Model. KF suffered brain damage from a motorcycle accident that damaged his short-term memory. KF's impairment was mainly for verbal information - his memory for visual information was largely unaffected.

This shows that there are separate STM components for visual information (VSS) and verbal information (phonological loop). However, evidence from brain-damaged patients may not be reliable because it concerns unique cases with patients who have had traumatic experiences.

One limitation is the fact that little is known about how the central executive works. It is an important part of the model but it’s exact role is unclear.

Another limitation is that the model does not explain the link between working memory and LTM.

Research Study for WM

AO1 or AO3

Research studies can either be knowledge or evaluation:

  • If you refer to the procedures and findings of a study, this shows knowledge and understanding.
  • If you comment on what the studies shows, and what it supports and challenges about the theory in question, this shows evaluation.

Baddeley and Hitch conducted an experiment in which participants were asked to perform two tasks at the same time (dual task technique). A digit span task which required them to repeat a list of numbers, and a verbal reasoning task which required them to answer true or false to various questions (e.g. B is followed by A?).

Results: As the number of digits increased in the digit span tasks, participants took longer to answer the reasoning questions, but not much longer - only fractions of a second. And, they didn't make any more errors in the verbal reasoning tasks as the number of digits increased.

Conclusion: The verbal reasoning task made use of the central executive and the digit span task made use of the phonological loop.


Explanations for Forgetting

→Interference|Retrieval Failure

Interference

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Interference is an explanation for forgetting from long term memory – two sets of information become confused.

  1. Proactive interference (pro=forward) is where old learning prevents recall of more recent information. When what we already know interferes with what we are currently learning – where old memories disrupt new memories.

  2. Retroactive interference (retro=backward) is where new learning prevents recall of previously learned information. In other words, later learning interferes with earlier learning - where new memories disrupt old memories.

Proactive and retroactive Interference is thought to be more likely to occur where the memories are similar, for example: confusing old and new telephone numbers. Chandler (1989) stated that students who study similar subjects at the same time often experience interference. French and Spanish are similar types of material which makes interference more likely.

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Postman (1960) provides evidence to support the interference theory of forgetting. A lab experiment was used, and participants were split into two groups. Both groups had to remember a list of paired words – e.g. cat - tree, jelly - moss, book - tractor. The experimental group also had to learn another list of words where the second paired word if different – e.g. cat – glass, jelly- time, book – revolver. The control group were not given the second list.

All participants were asked to recall the words on the first list. The recall of the control group was more accurate than that of the experimental group. This suggests that learning items in the second list interfered with participants’ ability to recall the list. This is an example of retroactive interference.

Although proactive and retroactive interference are reliable and robust effects, there are a number of problems with interference theory as an explanation of forgetting.

First, interference theory tells us little about the cognitive processes involved in forgetting. Secondly, the majority of research into the role of interference in forgetting has been carried out in a laboratory using lists of words, a situation which is likely to occur fairly infrequently in everyday life (i.e. low ecological validity). As a result, it may not be possible to generalize from the findings.

Baddeley states that the tasks given to subjects are too close to each other and, in real life; these kinds of events are more spaced out. Nevertheless, recent research has attempted to address this by investigating 'real-life' events and has provided support for interference theory. However, there is no doubt that interference plays a role in forgetting, but how much forgetting can be attributed to interference remains unclear.

Semantic memory more resistant to interference than other types of memory.


Retrieval Failure

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Retrieval failure is where information is available in long term memory but cannot be recalled because of the absence of appropriate cues. Types of cues that have been studied by psychologists include context, state and organisation

When we store a new memory we also store information about the situation and these are known as retrieval cues. When we come into the same situation again, these retrieval cues can trigger the memory of the situation. Retrieval cues can be:

  • Context - external cues in the environment, e.g. smell, place etc. Evidence indicates that retrieval is more likely when the context at encoding matches the context at retrieval.

  • State - bodily cues inside of us, e.g. physical, emotional, mood, drunk etc. The basic idea behind state-dependent retrieval is that memory will be best when a person's physical or psychological state is similar at encoding and retrieval.

    For example, if someone tells you a joke on Saturday night after a few drinks, you'll be more likely to remember it when you're in a similar state - at a later date after a few more drinks. Stone cold sober on Monday morning, you'll be more likely to forget the joke.

  • Organisation - Recall is improved if the organisation gives a structure which provides triggers, eg categories.

Evaluation (AO3)

According to retrieval-failure theory, forgetting occurs when information is available in LTM but is not accessible. Accessibility depends in large part on retrieval cues. Forgetting is greatest when context and state are very different at encoding and retrieval. In this situation, retrieval cues are absent and the likely result is cue-dependent forgetting.

A number of experiments have indicated the importance of context-based (i.e. external) cues for retrieval. An interesting experiment conducted by Baddeley indicates the importance of context setting for retrieval.

Baddeley (1975) asked deep-sea divers to memorize a list of words. One group did this on the beach and the other group underwater. When they were asked to remember the words half of the beach learners remained on the beach, the rest had to recall underwater.

Half of the underwater group remained there and the others had to recall on the beach. The results show that those who had recalled in the same environment (i.e. context) which that had learned recalled 40% more words than those recalling in a different environment. This suggests that the retrieval of information is improved if it occurs in the context in which it was learned.

A study by Goodwin investigated the effect of alcohol on state-dependent (internal) retrieval. They found that when people encoded information when drunk, they were more likely to recall it in the same state.

For example, when they hid money and alcohol when drunk, they were unlikely to find them when sober. However, when they were drunk again, they often discovered the hiding place. Other studies found similar state-dependent effects when participants were given drugs such as marijuana.

People tend to remember material better when there is a match between their mood at learning and at retrieval. The effects are stronger when the participants are in a positive mood than a negative mood. They are also greater when people try to remember events having personal relevance.

The ecological validity of these experiments can be questioned, but their findings are supported by evidence from outside the laboratory. For example, many people say they can't remember much about their childhood or their school days. But returning to the house in which they spent their childhood or attending a school reunion often provides retrieval cues which trigger a flood of memories.


Eyewitness Testimony

→Misleading Information|Anxiety

Misleading Information

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Loftus and Palmer investigated how misleading information could distort eyewitness testimony accounts.

Procedure: Forty-five American students formed an opportunity sample. This was a laboratory experiment with five conditions, only one of which was experienced by each participant (an independent measures experimental design).

Participants were shown slides of a car accident involving a number of cars and asked to describe what had happened as if they were eyewitnesses. They were then asked specific questions, including the question “About how fast were the cars going when they (hit/smashed/collided/bumped/contacted ) each other?”

Findings: The estimated speed was affected by the verb used. The verb implied information about the speed, which systematically affected the participants’ memory of the accident.

Participants who were asked the “smashed” question thought the cars were going faster than those who were asked the “hit” question. The participants in the “smashed” condition reported the highest speeds, followed by “collided”, “bumped”, “hit”, and “contacted” in descending order.

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The research lacks mundane realism, as the video clip does not have the same emotional impact as witnessing a real-life accident and so the research lacks ecological validity.

A further problem with the study was the use of students as participants. Students are not representative of the general population in a number of ways. Importantly they may be less experienced drivers and therefore less confident in their ability to estimate speeds. This may have influenced them to be more swayed by the verb in the question.

A strength of the study is it's easy to replicate (i.e. copy). This is because the method was a laboratory experiment which followed a standardised procedure.


Anxiety

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When we are in a state of anxiety, we tend to focus on whatever is making us feel anxious or fearful, and we exclude other information about the situation. If a weapon is used to threaten a victim, their attention is likely to focus on it. Consequently, their recall of other information is likely to be poor.

Clifford and Scott (1978) found that people who saw a film of a violent attack remembered fewer of the 40 items of information about the event than a control group who saw a less stressful version. As witnessing a real crime is probably more stressful than taking part in an experiment, memory accuracy may well be even more affected in real life.

However, a study by Yuille and Cutshall (1986) contradicts the importance of stress in influencing eyewitness memory. 21 witnesses observed a shooting incident in Canada outside a gun shop in which 1 person was killed and a 2nd seriously wounded. The incident took place on a major thoroughfare in mid-afternoon.

All of the witnesses were interviewed by the investigating police, and 13 witnesses (aged 15-32 yrs) agreed to a research interview 4-5 months after the event. The witnesses were also aksed to rate how stressed they had felt at the time of the incident, using a 7 point scale. The eyewitness accounts provided in both the police and research interviews were analysed and compared.

The results of the study showed the witnesses were highly accurate in their accounts, and there was little change in amount or accuracy of recall after 5 months. The study also showed that stress levels did not have an effect on memory, contrary to lab findings.

All participants showed high levels of accuracy, indicating that stress had little effect on accuracy. However, very high anxiety was linked to better accuracy. Participants who reported the highest levels of stress were most accurate (about 88% accurate compared to 75% for the less-stressed group).

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One strength of this study is that it had high ecological validity compared with lab studies which tend to control variables and use student populations as research participants.

One weakness of this study was that there was an extraneous variable. The witnesses who experienced the highest levels of stress where actually closer to the event (the shooting) and this may have helped with the accuracy of their memory recall.


The Cognitive Interview

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The cognitive interview involves a number of techniques:

Context reinstatement

  • Trying to mentally recreate an image of the situation, including details of the environment, such as the weather conditions, and the individual’s emotional state including their feelings at the time of the incident.

Recall from a changed perspective

  • Trying to mentally recreate the situation from different points of view e.g. describing what another witness present at the scene would have seen.

Recall in reverse order

  • The witness is asked to describe the scene in a different chronological order e.g. from the end to the beginning.

Report everything

  • The interviewer encourages the witness to report all details about the event, even though these details may seem unimportant.


The Enhanced Cognitive Interview

The main additional features are:-

  • Encourage the witness to relax and speak slowly.

  • Offer comments to help clarify witness statements.

  • Adapt questions to suit the understanding of individual witnesses.

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One limitation is the cognitive interview is that it's time consuming to conduct and takes much longer than a standard police interview. It is also time consuming to train police officers to use this method. This means that it is unlikely that the 'proper' version of the cognitive interview is used.

Another limitation is that some elements of the cognitive interview may be more valuable than others. For example, research has shown that using a combination of 'report everything' and 'context reinstatement' produced better recall than any of the conditions individually.

A final criticism is that police personnel have to be trained and this can be expensive and time consuming.

Geiselman (1985) set out to investigate the effectiveness of the cognitive interview. Participants viewed a film of a violent crime and, after 48 hours, were interviewed by a policeman using one of three methods: the cognitive interview; a standard interview used by the Los Angeles Police; or an interview using hypnosis.

The number of facts accurately recalled and the number of errors made were recorded. The average number of correctly recalled facts for the cognitive interview was 41.2, for hypnosis it was 38.0 and for the standard interview it was 29.4.

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