Duration of STM
Duration refers to how long a memory lasts before it is no longer available.
STM- Short term memories dont last very long. About 2 minutes.
An example would be like trying to remember a 7 digit phone number. It is maintained in STM by repetition until the number is dialed and then it is forgotten. The way people retain it for longer is to rehearse it until it becomes long term.
Peterson and Peterson (1959)- Tested recall of 24 students. Experimenter said nonsense trigram followed by 3 digit number eg WRT 303. After hearing the syllable and number, participant had to count backwards from number in 3s or 4s until told to stop. They then were asked to recall nonsense syllable. Counting backwards prevents rehearsal. Participants given 2 practice trials followed by 8 trials. On each trial time spent counting back was different: 3,6,9,12,15 or 18 seconds. Remembered about 90% on 3 second interval and 2% on 18 second interval. Suggests when rehearsal is prevented STM lasts about 20 seconds.
Criticsm of this study is that its only looking at the memory for syllables and words.
More recent study by Nairne et al found items could be recalled as long as 96 seconds.
Duration of LTM
LTM- Memories that arent STM. Anywhere from 2 minutes to 100 plus years.
Your memory for events that happend in the past.
Shepard (1967) tested duration. Showed 612 memorable pictures. Hour later participants were shown them plus other pictures and they showed almost perfect recall. 4 months later still able to remember 50% of photos.
Capacity and encoding
Capacity is the measure of how much can be held in memory. Measured in terms of bits of information ie chunks.
Encoding is the way information is changed so that it can be stored in memory. Information enters brain via senses. It's then stored in various forms eg visual codes or acoustic codes.
Capacity of STM
Miller- seven plus or minus two. Concluded that span of immediate memory is 7. People can cope reasonably well counting 7 ots but not many more. Same true for letters, numbers or words. Miller also found people can recall 5 words as well as they can 5 letters we chunk things together to remember more.
Simon- found that people had shorter memory span for larger chunks like 8 word phrases than smaller chunks like one syllable words. Shows the size of the chunks matter.
Cowan- more recently found STM likely to be limited to about 4 chunks.
Encoding in STM and LTM
Acoustic encoding involves encoding info in terms of the way it sounds.
Semantic encoding involves encoding info in terms of its meaning.
Baddeley tested effects of acoustic and semantic encoding on short and long term recall. Gave participants list of words that were acoustically similar or dissimilar and words that were semantically similar and dissimilar. Found participants had trouble remembering acoustically similar words in STM and found semantically similar words posed little problem for STM.
In general STM relies on acoustic coding. However, some experiments show that visual codes also used. Brandimote- found participants used visual coding when given a visual task and prevented from using verbal rehearsal. Normally we translate images into verbal code in STM but as verbal rehearsal was prevented they used visual codes.
Multi Store Model of Memory
A model of memory is a representation based on evidence available. Provides us with an analogy of how memory works.
Multi store model is an explanation of how memory processes work.
First described by Atkinson and Shiffrin (1968)
In the model there are 3 stores, Sensory memory, Short Term memory and Long term memory.
Sensory memory made up of our sense eg eyes and nose. They constantly recieve info but most gets no attention. If attention is focused on 1 of the stores the data is transferred to STM. Attention is first step to remembering things.
Info held in STM is in fragile state. Will disapear quickly if its not rehearsed. Will also disapear if new info enters, displacing it. This happens because STM has limited capacity (about 4 chunks).
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Multi Store Model of Memory continued
Second step is moving info from STM to LTM. Atkinson and Shiffrin said this also happens through rehersal.
More something is rehearsed the more lasting the memory will be. This kind of rehearsal. This kind of rehearsal is maintenance rehearsal which is largely verbal.
So the multi store model is a description of how memory works in terms of 3 stores. Your senses (sensory memory), STM (limited capacity, short duration) and LTM (unlimited capacity and duration). Attention and rehearsal explain how data is transferred.
Evidence for 3 separate memory stores
Key feature of MSM is proposal that memory can be separated into 3 distinct stores.
The sensory store- Sperling showed participants grid of digits and letters for 50 milliseconds. They were asked to write down all 12 items or they were told they would hear a tone immediatley after being shown and they should just write down that row. When asked to report whole thing recal was pooer (5 items recalled 42%) than when asked for 1 row (3 items recalled 75%). Shows info decays rapidly in sensory store.
Serial position effect- Glanzer and Cuntiz showed that words can be remembered better at the beginning of the list and the end. Primary and Recency effect. Primary effect occurs because first words you hear and therefore best rehearsed. Recency effect occurs because they are still in STM when you start recalling list.
Areas of brain associated with STM and LTM- Using MRi and PET scans. Beardsley showed prefrontal cortex active when working on task in STM. Squire et al found hippocampus active when working LTM.
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Evidence for 3 separate memory stores continued
Case studies-Case of HM- brain damage caused by operation to remove hippocampus tor reduce epilepsy. Personality and IQ remained but could not make new long term memories, though could remember things from before surgery. Suggests hippocampus may act as gateway for memories.
Evaluating the multi store model
1. Strong evidence of 3 seperate stores. Suggests the basis of the MSM is sound.
2. Provides an account of memory in terms of structure and process ie the 3 stores and rehearsal.
3. MSM has clear predictions about memory which means psychologists can conduct studies to test it. This is a strength because it pushes them into researching so they can find out more about human behaviour.
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1. Main criticism is that it oversimplifies structure and processes.
2. STM and LTM are not unitary- MSM suggests that STM and LTM operate in single fashion whereas evidence suggests this is not true. Shown in case of KF. KF suffered brain damage which made it difficult to deal with verbal info in STM but normal ability to process visual info. Suggests that STM is not a single store.
Schachter suggests 4 types of long term stores: Semantic memory (memory for knowledge), Episodic memory (for what you did yesterday etc), Proceduarl memory (for how to do things) and Perceptual representation system.
3.Rehearsal vs processing- research shown that maintenance rehearsal not only way of making enduring memories. Craik and Lockhart suggested enduring memories created by processing rather than through maintenance rehearsal. Things that are processed more deeply are more memorable because of the way they are processed. Shallow processing (Is the word printed in capitals), Phonemic processing (does the word rhyme with train) and Semantic processing (is the word a type of fruit?) Participants remembered most words from condition
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4. MSM suggests STM is involved before LTM. Logie said that STM relies on LTM there cannot come first. eg AQABBCITV. To chunk this you need to recall meaningful groups of letters which are stored in LTM.
Working memory model
WMM is an alternative model to the MSM.
It looks at one aspect of memory- Short Term.
Baddeley and Hitch first described it.
They felt that STM was not just 1 store but several because:
1.If you do 2 things at the same time and they are are both visual you perform them less well than you would if you did them seperately.
2.If you do 2 things, 1 being visual and the other involves sound then there is no interference. You do them as well simultaneously as you would do seperatley.
Suggests there is one store for visual and one store for sounds.
Working Memory Model Components
CENTRAL EXECUTIVE- Key component. Function is to direct attention to paticular task, determening how "resources" are allocated to tasks. Resources are 3 systems stated below. Data arrives from sense or LTM. Central exec has limited capacity (cant attend to too many things at once)
PHONOLOGICAL LOOP- Limited capacity. Deals with auditory info and preserves order of info. Baddeley further divided it into phonological store and articulatory process. Phonological store holds words you hear and articulatory process used for words that are heard or seen. Words are silently repeated (form of maintenance rehearsal)
VISUO SPATIAL SKETCHPAD- used when planning a spatial task eg moving from room to room. Visual/spatial info stored here. Visual is what things look like. Spatial is relationship between things. Logie suggested it could be futher divided into visual cache and inner scribe which deals with spatial relations.
EPOSODIC BUFFER- Baddely added because he realised needed a more general store. Other stores deal with specific info. Central exec has no capacity, so there was nowhere to hold info that relates to both visual and acoustic. ts an extra storage system. Limited capacity. It intergrates info from all other stores and LTM.
Evidence Supporting the WMM
1. Doing 2 tasks using same component- Hitch and Baddeley- showed that doing 2 tasks that use same component causes difficulty. Also said that when different components used performance is not affected.
2. There is evidence for 4 seperate stores:
Central exec- Activity in CE should be increased when person has to do 2 tasks simultaneously.. Bunge used fMRI to see which parts most active when doing 2 tasks . Same areas of brain active in either dual or single task but there was more activation in dual task indicating increased attentional demands.
Phonological loop-/Articulatory process- Phonological loop explains why word length effect occurs. People cope better with short words than long in STM. Seems PL holds the amount of info that you can say in 2 seconds (Baddeley). Longer words cant be rehearsed on PL because they dont fit. However, word length effect disappears if person is given articulatory supression task. This is because the task ties up articulatory process and means you cant rehearse the shorter words quicker than the longer words so word length effect disappears.
Evidence Supporting the WMM
Visup spatial sketchpad- Baddeley showed existence of it. Particpants given visual tracking task. At same time given 1 of 2 tasks. Task 1 was to describe angles on the letter F. Task 2 was to perform verbal task. Task 1 was difficult but not task 2 because the 2nd task involved 2 different components.
Eposodic buffer- Baddeley found that recall was better for related words than unrelated words. Supports idea of immediate memory store for items that are not visual nor phonological and that draw on LTM.
3. Evidence from brain damaged patients- KF- showed STM works independently of LTM as he had no problem with long term learning but had problems with short term memory
Evaluating Working Memory Model
STREGTHS OF WMM
1. Model explains obervations made by psychologists like word length effect.
2. Large amount of evidence to support it, especially recent studies which show links between certain tasks and activation parts of brain demonstrating components of WMM.
3.Continuing development of the model reflects the shift from seeing memory as 1 activity to being able to distinguish different types of memory. In 1960's psychologists tried to locate where memory was in brain. MSM offered first step in right direction in identifying some sub components of memory. WMM has continued this refientment for futher components of memory.
4. Large eviedence for a breif memory store. WMM gives better account than the STM component in the MSM. This is because it describes the STM as not a unitary store but a number of components whereas the MSM does not.
5. MSM only includes maintenance rehearsal as the only way to keep info. The MSM emphasies processing info as well.
Evaluating Working Memory Model
1. Central exec- Feels it is too vague and doesnt really explain anything. Not sure exactly what it is. Also feel that it is not just 1 component- case of EVR- performed reasoning tasks well which suggest CE intact but had trouble making decisions which suggest CE not wholly intact.
2. Some key evidence fro WMM comes from cases of people with brain damage. This is a problem because you cannot make before and after comparisons so you dont know wether changes are caused by the damage. Also the process of brain injury is traumatic which may in itself change behavoiur.
What is EWT?
Use of eyewitnesses to give evidence in court concering identity of someone who has commited a crime.
Eyewitness memory goes through 3 stages:
1. Witness encodes details of people and events in LTM. Encoding may be partial or distorted- crimes happen fast, at night and can be violent.
2.Witness retains info for period of time. Memory may be lost/modified during retention. Other activities between encoding and retrival may interfere.
3.Witness retrives memory. During reconstruction of memory retrival clues or nature of questioning may affect acuracy.
Studies of acuracy of EWT
Weakness- Loftus and Palmer- looked to see if leading questions distorted acuracy of witness recall. Students shown7 films of traffic acidents. After each film they were given questionaire which asked them to describe the accident and then answer series of questions. Was 1 critical question "About how fast were cars going when they hit each other" 1 group given this question. Other 5 groups given the verbs smashed, collied, bumped, contacted or hit. Group given word smashed estimated higher speed. Group given word contacted estimated loer speed.
Strength- Yullie and Cutshall- interviewed 13 people who witnessed armed robbery. Interviews took place 4 months after crime and included 2 misleading questions. Despite this they provided accurate recall which matched their inital description. Suggests post event info may not affect memory in real life EWT.
Role of Misleading Information
Study by Loftus and Palmer suggests questioning can have effect on witness answer to question. Possible post event info may alter info before its stored. They did another study- participants divided into 3 groups and shown film of car acident. Group 1 given verb smashed, group 2 hit and group 3 did not have any question about speed of vechicle. Participants returned 1 week later and asked questions including "did you see any broken glass" .
Does misleading questions affect way info is stored? Study by Bekerian and Bowers showed that misleading questions dont affect participants memory. Suggests misleading questions affect retrival of memory rather than their storage.
Deffenbacher- meta anlysis of 18 studies showed that high levels of anxiety negatively affected accuracy of EWT.
However some studies show that aniexty can have positive impact.
Study byChristianson and Hubinette- questioned 58 real witnesses to a robbery. Those who had been threatend remembered more and were more accurate in recall than those who were onlookers as they were more emotionally aroused.
Yerkes- Dodson law- says that performance improves with increase in arousal up to a certain optimum point and then declines with futhre increase.
Weapon focus effect- in violent crimes, arousal may focus attention on central details eg a weapon. Loftus et al identified weapons focus effect. 2 conditions, one involving weapon the other not. Condition 1 (less violent) people were 49% accurate in identifying man. Condition 2 (more violent) people were 33% accurate. Suggests weapon may have distracted them.
Age of Witness
Age differences in accuracy:
Parker and Carranza- compared ability of primary school and college students to identify a target individual. In photo identification, child more likely to choose somebody than adult although they were more likely to make errors.
Memon et al- studied acuracy of young and older eyewitnesses. When delay between incident and identification was short, was no difference in 2 groups. When delayed by 1 week, older witnesses less accurate.
Age of witness
The owen age bias:
Most studies shown older adults poorer at eyewitness memory. However, may result from stimuli typically used in these studies. Most studies used college students to correctly identify faces of similar aged targets. However, older adults where asked to identify college aged student targets. As a result, much of the work done on age differences in ERT has ignored possibility that participants may simply have better memory for faces of their own age.
Explaining the own age bias:
Findings from this research consistent with own race bias where people better at identifying people from their own ethinic group. The DIFFERENTIAL EXPERIENCE HYPOTHESIS suggests that the more contact we have with particular age group or ethnic group the better our memory would be for such individuals.
The Cognitive Interview
Is a procedure designed for police interviews. 2 main forces behind development of CI. First being need to improve effectiveness of police interviewers when questioning. Second was to apply results of psychological research to this area.
Fisher and Geiselman applied knowledge of memory and related to way interviews are carried out and came up with the CI. Found people remembered events better when provided with retrieval cues. 4 stages to interview:
1. Report everything even though it may seem irrelevant.
2.Mental reinstatement- witness encourage to mentally recreate environment and contacts from incident.
3. Changing the order- interviewer may try alternative ways through timeline of events eg reverse the order.
4. Changing the perspective- asked to recall incidents from different perspectives eg perception of a passer by.
Research into effectiveness of cognitive interview
- Meta analysis of 53 studies found an increase of 34% of amount of correct info given under CI compared to standard interview- done by Kohnken et al. However, most studies used volunteers usually students in a lab which may not be reliable as it's not real life.
Evaluation of cognitive interview
- Problem with evaluating CI is that its no longer 1 procedure but a collection of techniques.
- For example not all Police use every part of the CI. Most only use reinstate context and report everything.
- Kebbell and Wagstaff interview the police and found that the technique requires more time than is often available and so they instead use strategies aimed to limit eyewitness to report minimum amount police feel necessary.
- Also enhanced version of CI causes more demand on the interviewer. As a result qauntitity and qaulity of training of CI has become a big issue.
- Memon found that interviewers were only given a 4 hour training session which did not produce any significant increases compared to standard technique.
Strategies for memory improvement
A mnenomic isany structured technique used to help people remember and recall info.
- Acronym- Where the inital letter of other words is used to make word or sentence.
- Acrostic- poem or sentence where 1st letter in each line or word used Eg many vile earthlings.
- Rhymes- groups of words with an identity and rhythm. eg Tune of twinkle twinkle helps to remember letters of alphabet.
- Chunking- involves dividing long string of info into memorable chunks.
Stratergies for memory improvement
VISUAL IMAGERY MNEMONICS
- Best know is method of loci first described by Greeks. The method requires learner to associate parts of info to be recalled with different places (eg rooms in house) in the order they need to be recalled.
- Keyword method is used when trying to associate 2 pieces of info. Eg Trying to learn a foreign language and the English equivalent. Spanish word for horse is caballo which is pronounced cob-eye-yo. Keyword could be eye so you could visualise a horse with a big eye.
- Mind maps- making notes of info in form of drawing usually branches. Each page of notes should be unique and distinctive.
Explaining how mnemonic techniques work
ROLE OF ORGANISATION
By organising data we establish links that help recall. Word assossciations and visual images help create links. Mnenomics acelerate the process of association by lniking new info with memory hooks.
If your information is organised you can find the information more quickly.
ROLE OF ELABORATIVE REHEARSAL
Memory research has shown enduring memories created through process of elaboration. Mnemonics make us elaborate info.
Amount of rehearsal is important but nature of rehearsal is more important.
Explaining how mnemonic techniques work
DUAL CODING HYPOTHESIS
Paivio suggested words and images are processed seperatley. He said concrete words, which can be made into images, are double encoded into memory. Coded once as verbal symbols and a second time as image symbol. Double encoding increases likeihood that it will be remembered. This can be linked to the phonological loop.