The Multi-store Model:
- There are three seperate stores - sensory, short-term (STM) and long-term (LTM) .
- Sensory memory has a store for each of the senses, e.g. hearing, vision.
- STM and LTM are unitary stores- each operates like a single unit with no seperate compartments.
- entering the memory system passes through the stores in a fixed sequence
- can be lost at any stage
- usually has to be recorded as it passes from store to store
- can only pass from sensory memory to STM if given attention
- if not given attention is lost (through decay)
- can only pass from STM to LTM if we rehearse (repeat) it
- if not rehearsed enough, it is lost (through decay and displacement)
- Each store is different in terms of encoding, duration and capacity.
Research into Capacity in STM- Jacobs;Miller:
Method: the digit span technique.
Participants given strings of unrelated digits that increase by one digit every time.
Digit span measured at the point where participants can no longer recall the digits in the correct sequence.
- STM capacity is very limited
- Digit span is 7+ or -2
- Span can be increased by chunking i.e. by putting several items into a meaningful 'chunk'
Digit span is an artificial measure- not a real-life situation.N
o independent measure of a 'chunk'. Number of chunks we can recall depends on various factors.
Baddeley and others have found that we can recall from STM as many items as we can pronounce in 2 seconds, so capacity might be better measured in terms of pronunciation time rather than no. of items
It is hard in experiments to exclude the influence of LTM.
Research into Duration in STM- Peterson and Peters
Method: participants very briefly presented with consonant trigram.
Asked to count backwards in threes from a given digit (to prevent rehearsal)
On each trial (i.e. with a different trigram each time) stopped after an interval ranging between 3 and 18 seconds and asked to recall trigram correctly.
- STM has very brief duration when rehearsal is prevented
- Participants could recall about 80% of the trigrams correctly after 3 seconds but less than 10% after 18 seconds
Research is based on artificial stimuli like trigrams- not real life.
Peterson technique might not be an accurate measure of duration because:
- counting backwards in 3s was used to prevent rehearsal, but it might have displaced the trigram
- Participants had to carry out several trials. Accuracy of recall became worse as the trials went on. It might be that trigrams presented early on caused confusion for later trigrams.
- Amount of information seems to be crucial. A single 3 letter word (DOG) can be recalled easily after 18 seconds without rehearsal, but a 3 letter nonsense trigram (QKM) cannot.
Research into Encoding in STM- Conrad:
Method: showed participants a random sequence of 6 consonants very briefly on a screen
similar sounding (B,T,D etc.) and different sounding (Y, R, F)
Participants then asked to write the consonants down in the correct order
- STM uses mainly acoustic coding
- Participants found it more difficult to recall and made more errors on the lists of similar sounding consonants
Research used artificial stimuli- not real life
Conrad used university students as his participants- might not be a representative sample.
Conrad only used consonants- these can only be represented in acoustic or visual code so he was not able to rule out semantic coding as a method of encoding in STM.
However, Baddeley carried out a similar study using words and concluded that Conrad's findings were correct, i.e. acoustic coding is the preferred method of encoding in STM.
Research into Duration in LTM- Bahrick:
Tested nearly 400 American high-school graduates on their memory for former schoolmates
Used a variety of memory tests- recognition of photos, matching names to photos and recalling names with no photo cue
- Participants preformed well up to 34 years after they had left high school
- Memory performance was generally better on recognition tasks than recall tasks
- Performance declined after 47 years
The study looked at how memory works in real life not in laboratory settings
It is difficult to control extraneous variables when investigating duration of LTM
Information in LTM can last for a lifetime, but it sometimes needs retrieval cues to get it
Later research suggests that information lasts longer if very well processed and if the material is thoroughly understood rather than learned by rote.
Research into Encoding in LTM- Baddeley:
Constructed lists of words in 4 categories: 1) sound similar,
(2) don't sound similar,
(3) mean the same,
(4) don't mean the same
Presented 10 words from each list to participants and after each presentation, prevented rehearsal
recall was tested after 20 minutes
- Participants performed least well on the lists where the words were similar in meaning
- Baddeley concluded that this was because LTM codes for meaning (semantically)
This study used real words rather than meaningless consonants, but it was still carried out in a laboratory and so was artificial. This reduces the validity.
We can instantly recognise sounds like police sirens- suggests that we can code acoustically in LTM as well.
Other research evidence suggests, although semantic encoding is the preferred form, we can code visually in LTM as well.
Strengths of the Multi-store Model:
- Neuropsychological evidence
- Case studies of HM and Wearing show how STM can function relatively normally while transfer to and retrieval from LTM is impossible
- In another case study KF had an intact LTM but a grossly impaired STM
- Patients with Alzheimers disease can perform reasonably on STM but not LTM tasks
- Brain scanning techniques have shown different areas activated in STM and LTM tasks
- Laboratory evidence
- Duration of STM is limited to a few seconds (Petersons) LTM can last a lifetime (Bahrick)
- Capacity of STM is shown to be limited to between 5 and 9 items or chunks (Miller) whereas LTM capacity is limitless
- Acoustic coding is the preferred form in STM (Conrad) whereas semantic coding is the preferred form in LTM (Baddeley)
- Influential theory based on computer modelling-provided impetus for further important research
- Key aspect is the division of memory into two major types- short term and long term- still useful
- Large amount of research evidence supporting STM/LTM distinction
- The free recall task (Glanzer and Cunitz) shows how STM and LTM function differently. It also supports the MSM in showing how rehearsal moves information from STM to LTM
Weaknesses of the Multi-store Model:
- Is rehearsal the only way of getting information into LTM?
- KF could put new information into LTM even though his STM wasn't working properly- there must be some other route into LTM
- Memories for shocking events show to imprint directly into LTM without rehearsal
- There are many techniques to improve memory that do not depend on rehearsal
- Are there different ways of interpreting research studies?
- KF can be used to support the model or cast doubt on it, as he can put items into LTM without processing them in STM first
- Digit span is about 7 items. Miller thought this was because we only have this amount of space in STM and Baddeley thought it was because we can only remember as many items as we can say in 2 seconds i.e. STM is limited in terms of time rather than space
- Does information flow through the system in a fixed sequence?
- Information from LTM sometimes has to be activated before the final stages of processing in STM can occur
- Are STM and LTM single stores with no divisions?
- Baddeley shows in research for the WMM that STM is divided into several components
- Is human memory that simple?
- The MSM is too simple- can't explain why we remember some things better than others
Working Memory Model:
- It explains how short-term memory works
- It consists of several different components ( STM is not unitary as in MSM)
- Each component has a particular function- includes not only storage but manipulation and analysis of information
- Central executive is the key component that oversees and coordinates the other components (slave systems)
- There is a two-way flow of information between the central executive and the slave systems
- The slave systems have seperate responsibilities and work independently
- The phonological loop is subdivided into the phonological store (inner ear) and the articulatory loop (inner voice). It is a limited capacity, temporary storage system for holding visual and spatial information
- The model has been modified over the years to take account of research findings, and new components ( the episodic buffer ) have been added.
- The episodic buffer combines information from the other stores into a single representation
- The episodic buffer was added in 2000 because a number of research findings were hard to explain without it
Supporting Research of the Working Memory Model:
- Baddely and Hitch- Gave participants a dual task:
- A reasoning task
- Reading aloud
- Participants could do both tasks very well simultaneously
- STM must have different components that can process more than one type of information at a time
- Baddeley et al- 1973- Gave participants a dual task to do simultaneously:
- A tracking task
- A visual imagery task
- Participants were much poorer at the dual task performed alone
- Concluded that both tasks needed to be done in the visuo-spatial sketchpad so were competing for the same limited resources
- Baddeley et al-1975- Gave participants brief visual presentations of lists of words,
- either long or short words,
- Asked participants to recall the list immediately in correct serial order
- Participants could recall more short words than long words (word length effect)
- Concluded that the loop can hold as many items as can be said in 2 seconds. So the loop has a time limit rather than being limited by items
Strengths of The Working Memory Model:
- Very influential model-most cognitive psychologists now call STM working memory
- It has stimulated research and the model has been modified to account for new findings
- It has practical applications
- It is important in the development of reading and can help our understanding of dyslexia
- Working memory capacity can be used as a measure of aptitude for certain jobs
- It explains research findings better than the MSM
- Can explain how we can do more than one task simultaneously in STM e.g. reading aloud while visually tracking an object
- Explains how we can remember things without rehearsal
- It can account for individual differences in memory ability
- Research has shown that people differ in their working memory span and that they can score high on visual working memory tests but low on verbal working memory tests or vice versa
Weaknesses of The Working Memory Model:
The role of the central executive
- The most important component is the least well researched
- Baddeley agrees it is difficult to investigate the central executive
- We do not fully understand how it supervises and coordinates the slave systems
Failure to account for all sensory modalities
- Model does not make it clear how we deal with information from the smell and touch senses
- It also does not account well for our ability to process non-verbal sound such as music
The validity of some research findings
- Some critics say that we make assumptions from the model that might not be true. For example we assume that two tasks can be done simultaneously are processed in different parts of the WM, but we cannot do them together that they are competing for the same part of the WM. This is called a 'circular argument'.
Effects of Anxiety on Eyewitness Testimony (EWT)-
- Asked participants to sit outside a laboratory where they thought they were listening to a genuine exchange between people inside.
- Condition 1: overheard a friendly discussion and then saw a man come out of the room with greasy hands holding a pen
- Condition 2: overheard a hostile discussion and furniture being overturned and saw a man come out of the room holding a bloodstained knife.
Both sets of participants were asked to identify the man from 50 photos.
Participants who had witnessed the more violent scene were less accurate in identifying the man
Loftus concluded that this was because the heightened anxiety of the witnesses in the violent scene caused them to focus on the weapon and not take in other details (weapon effect)
This was a staged experiment, but it was similar to real life in that the participants thought they were waiting to take part in a different experiment so were not expecting to be called as a witness. There are ethical issues when participants are unexpectedly exposed to anxiety.
The findings of this study have been supported by other research e.g. Loftus and Christianson- people who were interviewed 6 months after seeing a traumatic filmed event could remember the essence of the event very well but had grossly impaired memory of the details surrounding it
Effects of Anxiety on Eyewitness Testimony (EWT):
Anxiety is a state of heightened arousal in response to some kind of threat or danger.
Chrisianson and Hubinette:
Surveyed 110 people who between them had witnessed 22 different bank robberies either as direct victims or as bystanders
The victims of the crimes who had been subjected to the greatest levels of anxiety were more detailed and accurate in their recall than the bystanders
This suggests that people react to anxiety-inducing events differently when they occur in real life rather than in a laboratory
Effects of Age on Eyewitness Testimony (EWT):
Flin et al: Asked children and adults questions about an incident they had witnessed- one day after the event and then 5 months after it.
- Recall was similar for adults and children after one day but significantly worse for children after a 5 month delay
- This decline in accuracy with time is important because court appearances are often a long time after the crime
Gordon et al: Reviewed a number of studies of child witnesses
- Children can recall accurately and in detail, but are more susceptible to misleading information
- Davies has disputed this. He thinks children can resist if they are questioned very sensitively.
Yarmey: Showed young and elderly adults a film of a staged event and asked questions about what they had seen
- 80% of elderly adults failed to mention a key detail ( attacker had a knife in hand)
- This was an artificial situation- it might not reflect how people react to a real life situation
Effects of Misleading Information on Eyewitness Te
Showed a film of a car accident and then asked questions about it. A crucial question was asked about the speed of the car. All groups were asked the same question but a different verb was used e.g. hit, smashed, bumped, collided, contacted
Participants who were asked the 'smashed' question produced by far the highest estimate of speed, while those hearing 'contacted' gave the lowest estimate of speed
A week later, participants in the 'smashed' condition were more likely than other participants to report seeing broken glass at the accident scene even though there was none
The verb used had significant effect on the speed estimate. It continued to affect recall after a delay of a week, suggesting that the false memory had become permanently lodged in the memory
Critics of the study suggested that participants might have been responding to demand characteristics
Effects of Misleading Information on Eyewitness Te
Showed participants film of events leading up to a car accident. One group was then asked questions consistent with the film. The second group were asked the same questions except for one concerning a barn ( there had been no barn in the film)
When recalling the film, 17% of the misled group reported seeing a barn but only 3% of the other group said they had seen it
Loftus concluded that the misled group had incorporated the false information about the barn into their original memory
Although the result was significant it is clear that not everybody in the misled group was affected by the post-event information
Fisher et al:
studied genuine interviews carried out by experienced police officers in Florida and found:
- Questions were brief, direct and closed
- Sequencing of questions often did not match the witnesses' own image of the event
- Police questioners often interrupted, not allowing witnesses to expand on their answers
On the basis of this kind of research, Geiselman developed the cognitive interview
He then added some features to make a version called the enhanced cognitive technique-
minimal distractions, active listening, ask open-ended questions, pause after each response, avoid interruption, adapt use of languae to suit witness and avoid judgemental comments.
Cognitive Interview Techniques:
Context reinstatement (CR):
Think yourself back to the scene of the event, What were you feeling, what had you just been doing what was the weather like, who was standing around, etc?
Report everything (RE):
Report everything you can think of about the event even if it seems trivial- it might have a bearing on the event or trigger your memory of something important.
Recall from changed perspective (CP):
Try to put yourself in the shoes of someone else at the scene and describe it from their point of view
Recall in reverse order (RO):
Report the details of the event from back to front or start with a particular aspect of the scene and work backwards or forwards from that
Research into Effectiveness of Cognitive Interview
Geiselman et al: Showed participants videos of a simulated crime. They tested recall by cognitive interview, standard interview or hypnosis.
Cognitive interview prompted the most information
However, Koehnken et al found that it produced more incorrect information than the standard interview
Fisher et al: Trained real detectives to use enhanced cognitive interview with real crime witnesses
They found that cognitive interview considerably increased the amount of information recalled compared to standard interviews
The study used real police officers and crime witnesses so lacked artificiality of some other studies
Milne and Bull: Tested each of the cognitive interview techniques singly or in combination
All four techniques used singly produced more information than the standard interview, but CR with RE the most effective combination
This confirmed the beliefs of the UK police that some techniques are more effective than others
Examples of Mnemonics:
Peg-word system: first learn the list of peg words, which each rhyme with a number up to 10 e.g. one is bun, two is shoe. Associate each word to be remembered with a peg word, If you want to recall a shopping list make a visual image of the first item, e.g. potatoes with the first peg word i.e. bun.
- You have to learn the peg-word list first
- It is only useful for lists which we rarely have to commit to memory
Method of loci: think of a familiar route e.g your house. Pick distinct places along the route (as many places as items you need to recall) Associate each item with a place on the route. When you come to recall, retrace your route and the item will be recalled
- same problems exist as with peg-word except this method is slightly more flexibe
Keyword method: used for learning foreign languages. when you are given a new word to learn, think of a similar-sounding English word and form an image of the two meanings. E.g. german word igel (pronounced eagle) means hedgehog. Picture an eagle swooping down to catch a hedgehog
- demonstrated effective in learning foreign words, only words not grammar
Strategies for Memory Improvement:
Verbal mnemonics: Used when it is important to recall the order of things eg. colours of the rainbow.
- Use acronyms- make up a word from the intial letter of the colour
- Rhymes or songs can also be used
Encoding specificity principle: You recall things better if you have cues available to you that were present when you first learned the material
- Evidence to suggest just imagining yourself back in the place is a powerful memory cue. remember that CR is one of the most successful CI techniques
- Recall seems to be better if you're in the same mood or physical state when you retrieve the memory as when you encode it
Active processing: Simple rote rehearsal can be effective if you have plenty of time to repeat the items and are not disturbed
- rehearsal is much more effective if it is elaborate- you need to think about the material to be learned and encode it semantically- setting up several associations in LTM and so have several retrieval routes