Memory: The process by which we retain information about events that have happened in the past.
STM: Your memory for events in the present or immediate past.
- Any information in the STM can disappear if not rehearsed.
- The result of verbal rehearsal is that STMemories are held in the STM and eventually become long-term.
- The STM measure duration in seconds.
- Capacity is less than 7 chunks.
- Acoustic and Visual encoding found in the STM
- Peterson(1959) conducted a study of the duration of STM of 24 university students.
Lab experiment with 24 university students who had to recall meaningless trigrams(SWD 452). To prevent rehearsal, participants were asked to count backwards in 3s or 4s from a specified random number until they say a red light. This is known as the brown peterson technique. Asked to recall trigrams after intrvals of 3,6,9,12,15 and 18 seconds.
- Found that participants remembered 90% when there was a 3s interval and 2% when there was an 18s interval.
- Suggesting that when rehearsal is prevented, STM lasts 20 seconds at most. Shows differentiation in terms of duration and supports the MSM or memory.
Criticism- not actually testing duration, when the participants were counting backwards, the trigram could have been displaced in the STM by the numbers, thus wiping out memory for the syllables.
-Marsh et al (1997) suggested that participants do not expect to be tested after this interval, forgetting may occur 2 seconds after. Suggesting that knowledge of STM duration may not be as clear-cut as thought.
-Nairne(1999) found that recall could happen 96 seconds after. Asked to recall same items in a trial. Interference between items in petersons study led to decrease in recall, suggesting that information remains in the stm for quite a while unless other information replaces it.
LTM: Your memory for events that have happened in the more distant past.
- Memory can last from 2 minutes to 100 years.
- LTM has unlimited capacity and duration.
- Duration is measured in days and years.
- Semantic(meaning) encoding is used in the LTM
- Tested duration of LTM. Showed participants 612 memorable pictures, one at a time. An hour later they were shown some of these pictures among a set of another and showed almost perfect recognition. Four months later they were still able to recognise 50% of the photos.
Bahrick et al(1975)
- Conducted in America. Demonstrated the considerable duration of LTM by asking people of various ages to put names to faces from their high school yearbook. 48 years on, people were 70% accurate.
Increasing the capacity of STM
- The magic number 7+-2.
- George Miller(1956)- wrote a memorable article 'The magic number seven plus or minus two' He concluded that the span of immediate memory is 7; people can reasonable coped well when counting seven dots which flashed onto a screen but not many more than this.
- The size of the chunk matters
- The size of the chunk affects how many chunks you can remember. Simon (1974) found that people had a shorter memory span for larger chunks, such as 8-word phrases, than smaller chunks, such as one-word syllable words.
- Jacobs(1887) used the 'digit span technique' to assess capacity of STM. He found that the average span for digits was 9.3 items, while it was 7.3 letters. Why was it easier to recall digits? Jacobs suggest that it may be because there are only 9 digits wheeas there are 26 letters.
Encoding in STM and LTM
Acoustic and Semanting encoding
- Acoustic coding involves coding information in terms of the way it sounds, and semantic coding involves coding information in terms of its meaning.
- Baddeley(1966) He gave participants lists of words which were acoustically similar or dissimilar and words which were semantically similar or dissimilar.
- He found that participats had difficulty remembering acoustically similar words in STM but not in LTM, whereas semantically similar words posed little problem for short-term recall but led to muddles long-term memories.
- STM appears to rely on an acoustic code for storing information. However, some experiments have shown that visual codes are also STM.
- Research has shown that encoding in LTM is not exclusively semantic. Frost (1972) showed that long-term recall was related to visual as well as semantic categories, and Nelson and Rothbart (1972) found evidence of acoustic encoding.
Multi Store Model
Sensory memory: several stores: eyes, mouth, nose, fingers and tongue etc. If attention is focused on one store then the data is transferred to STM.
Short-term memory: information here is in a 'fragile state' and will disappear quickly if not rehearsed or displaced. STM has a limited capacity.
Long-term memory: Moving data from STM to LTM is also done by rehearsal. The more the information is rehearsed, the better it is remembered(Atkinson and Shiffrin)
Evidence for MSM
Glanzer and Kunitz(1966) 'Serial position effect'
- Participants were given a list of 20 words, presented one at a time, and then asked them to recall any words they could remember.
- They tended to remember the words from the top of the list(a primacy effect) and the end of the list(a recency effect) but were less good at recalling the words in the middle.
- The primacy effect occurs because the first words are transferred into LTM because of rehearsal. The recency effect occurs because these words are in the STM when people start recalling the list. The words in the middle have been displaced by the recent words.
Case study of HM
- Different areas of the brain are involved in STM and LTM from their study of individuals with brain damage.
- HM, had brain damage after an operation to remove his hippocampus to relieve the severe epilepsy he suffered.
- HM could not form long-term memories though he could remember things from before the surgery.
- This suggest that the function of the hippocampus may function a 'memory' gateway through which new memories must pass before entering permanent storage in the brain for anything that happened since.
Limitations of MSM
Structures: STM and LTM are non-unitary stores.
- Evidence from non-unitary stores came from the case study of KF, reported by Shallice and Warrington(1970).
- KF suffered brain damage which resulted in difficulty dealing with verbal information in STM but a normal ability to process visual information.
- Suggesting the STM is not a single store.
- The MSM describes LTM as one single store, whereas evidence from patients with amnesia indicates that there are different kinds of long-term memory.
Schachter et al(2002) suggested there are 4 types of long-term stores.
- Semantic memory: General knowledge about anything, like the world
- Episodic memory: memory of what you did last week etc.
- Procedural memory: memory for riding a bicycle or learning how to read
- Perceptual representation system: memory related to perceptual priming- recognising specific stimuli which have been seen before. e.g TOBOGGAN and _O_O_GA_N
- Research has shown that maintenance rehearsal is not only the means by which enduring long-term memories are created.
Craik & Lockhart(1972)
- proposed a different kind of model to explain lasting memories.
- suggested that enduring memories are created by the processing rather than maintenance rehearsal: things that are processed more deeply are more memorable by the way they have been processed.
Craik & Tulving(1975)gave participants a list of nouns and asked a question about each word. There were three kinds of questions that each participant answered:
- Shallow processing: 'is this word in capital letters?'
- Phonemic processing: 'Does the word rhyme with "train"?'
- Semantic processing(deeper process of meaning): 'Is this word a type of fruit?
Participants remembered most of the words from condition 3 than 1, suggesting that deeper processing leads to enhanced memory.
This has led to a reformulation of the MSM, maintenance rehearsal has been replaced with elaborative rehearsal.
Working Memory Model
Baddeley and Hitch(1974)
- suggested that STM was not a single unitary store but a number of different stores.
- this is because, if you do two things at the same time which involves a visual and sound, this means there is no interference, and you do them as well simultaneously and you would separately.
- One store for visual processing and one store for processing sounds.
Working memory model
- Central executive: directs attention to particular tasks, determining at any time how 'resources' are allocated to tasks. The central executive has limited capacity. The 'resources' are listed below:
- Phonological loop: this too has limited capacity, it deals with auditory informtion and preserves the order of information.
- Baddeley(1986) further divided this to the phonological store: holds words you hear, like inner ear and articulatory process: used for wordss that are heard or seen. These words are silently repeated(looped) like an inner voice, a form of maintenance rehearsal.
- Visuo-spatial sketchpad: is used when you have to plan a spatial task, like getting from one room to another. Visual and/or spatial information is temporarily stored here. Visual information is what things look like, Spatial information is the relationship between things.
- Episodic buffer: Baddeley(2002) added the episodic buffer because he realised the model needs a general store. It is an etra storage system that has limited capacity. The episodic buffer integrates information from all the stores.
Evidence supporting the working memory model
- Case study of KF, Shallice and Warrington(1970) showed that STM works indepepndently to LTM, as he only had problems with immediate memory. His short-term memory of verbal information was lacking full function compared to his visual information. Thus his brain damage seemed to be restricted to the phonological loop.
Word length effect
- people cope better with remembering short words than long wording in memory. It seem that the phonological loop hold the amount of information that you can say in 2 seconds (Baddeley 1957a). This makes it hard to remember a long list of words such as 'association' compared to shords words like 'harm'. The longer words do not fit inside the phonological loop.
- The word length effect disappears if a person is given an articulatory suppression task, (if you are asked to say 'the the the' whilst reading the words) this repetitive task ties up the articulatory process and means you cant rehearse the shorter words more quickly than the longer ones, so the word length effect disappears.
Eye Witness Testimony-LOFTUS
LOFTUS AND PALMER(1974) Experiment 1.
- 45 students were shown 7 films of different raffic accidents. A questionnaire was given to recall the the accident. One specific question was altered to find if misleading information affected memory recall. 'How fast was the care going when they HIT eachother?' One group received this question and 5 groups were given the vers smashed, collided, pumped or contacted in the place of the word 'hit'.
This shows that the form of questioning can have a significant effect on a witness's answer to the question. Possible that post-event information had affected the material before it is stored, altering the memory of the event permanently.
Limitations of EWT
1. One limitation of this study is that it lacked ecological validity
- Participants saw film clips rather than being present at the real accident. They would therefore feel less emotionally involved and therefore paying less attention and less motivated to be accurate in their judgements. A study by Yuille and Cutshall (1986) involved real people who witnessed a real armed robbery. They found, despite the use of misleading information, wittnesses recall was still accurate after 4 months.This suggests that Loftus and Palmers study lacked ecological validity and the 'real life' EWT may be resistant to misleading information.
2. A second limitation of this study is that it doesnt show whether memory itself is altered
- The misleading information provided may have simply influenced the answer a person gave (a 'response-bias') but didnt actually lead to false memory of the event. If it is just a response-bias then it is not relevent to EWT.This suggests that further investigation is necessary to check whether memory was just altered or whether it was just a response-bias.
LOFTUS n palmer part 2
- In this second study, 150 students were shown films of car accidents and were asked questions about the accidents.
The participants were divided into 3 groups:
- (1) One group were askied the critical question with the verb 'smashed'
- (2) A second group was given the word 'hit'
- (3) The third group was a control group who were not asked a critical question
Participants were asked to return to the lab a week later and were asked questions involving broken glass, 'Did you see any broken glass?' There had been NO broken glass in any of the film clips but they were asked if they had seen some.
- Mean speed estimates were greater for the groups with the verb 'smashed' (10.46 mph) than 'hit'(8.0mph)
- More participants who had the verb 'smashed' reported seeing broken glass (16 out of 50) than other participants.7'hit' 6'control'.
- Evidence suggests that misleading information actually alters memory faster because the false memory of travelling faster, led participants to generate and expectation that there may be broken glass. (121 out of 150 recorded no broken glass)
Limitations of EWT (2)
1. One limitation of this study is that the problem of ecological validity still remains.
- Many 'real life' cases show the effects of misleading information on the accuracy of EWTIn cases where DNA has been used to identify a criminalm mistaken EWT identification has been seen as the largest single factor in mistaken convictions. Showing that LAB evidence has ecological validity.
EWT and anxiety- WEAPON FOCUS
Johnson and scott (1976)
This study investigated the effects of weapon focus on eye witness testimony. Participants were asked to sit on their own in a waiting room until it was there turn to be tested.
While sitting in the waiting room, the participant overheard two people in the next room.
- (1) High anxiety condition- Two people were having an argument with loud shouting and crashing items. Then one of the two people from the next room ran through the waiting room, covered in blood and holding a letter opener in blood.
- (2) Low anxiety condition- There was a low and quiet conversation in the next room and someone walked through the room holding a grease pen.
- In both conditions, the TARGET person walking through the room spoke one line and was only present for 4 seconds.
Participants were asked to identify the TARGET person from a set of 50 photographs.
Findings and Evalution of weapon focus
-High anxiety condition led to lower correct information.
- Participants who were exposed to the high anxiety condition were less successful in identifying the target individual (33% correct) than those in the low anxiety condtion (49% accurate)
-Very few noticed the pen but most noticed the letter opener
- Very few participants in the low anxiety condition even noticed the pen, where as in the high anxiety condition most participant noticed the letter opener.
-High anxiety meant focus on the weapon rather than the targets face.
- These results suiggest that focus on a threatening object may prevent awareness of other aspects of a crime scene, such as the criminals face. This would affect the accuracy of EWT.
1. ONE limitation is that weapon focus may not reduce accuracy of EWT. Loftus et al (1987) showed that weapon focus did not affect the ability to identify the target
EWT and Age
Children as witness
- Parker and Carranza (1989) compared primary school children and college students in their ability to correctly identify a target individual following a slide sequence of a mock crime. In the photo identification task, child witnesses had a higher rate of choosing than adult witness, although they were more likely to make errors than college students
Age difference in accuracy
- Yarmey (1993) stopped 651 adults in public places and asked them to recall physical characteristics of a young woman to whom they had spoken for 15 seconds 2 minutes earlier. (18-29 & 30-44) adults were more confident in their recall than older adults, there was no significant difference in accuracy of recall that could be attributed to the age group of witness.
CI is based on psychological understanding of memory to maximise detail and accuracy
Fisher & Geiselman(1992) argued that eye witness testimony could be improved if the police used better techniques when interviewing witnesses. Suggested they should be based on psychological insights into how memory works, and called it the cognitive interview.
1. REPORT EVERYTHING- Witnesses are encouraged to include every single detail of the event, even though it may seem irrelevant or the witness doesnt feel confident about it.
2. CONTEXT REINSTATEMENT-The witness should return to the original crime scene 'in their mind' and imagine the environment and their emotions.
3. REVERSE ORDER-Events should be recalled in a different chronological order, i.e from the final point back to the beginning, This is done to prevent people using their scripts and also prevents dishonesty.
4. CHANGE PERSPECTIVE-Witnesses should recall the incident from other peoples perspectives. For example how it wouldve appeared from another witnesses perspective.
Cognitive interview evaluation
1. Cognitive interview is time consuming
- police are reluctant to use this technique as it takes much longer than a standard police interview. The CI also requires special training and many forces have not been able to provide more than a few hours. Which means that it is unlikely that the proper version of the cognitive interview wouldve been used.
2. Cognitive interview increases inaccurate information
- CI techniques aim to increase the amount of correct information but the recall of incorrect information may also increase. Kohnken 1999 found at 81% increase of correct information but also a 61% increase in false information, when the ci was compared to the standard interview.
3. CI has increased effectiveness.
- Kohnken 1999 meta-analysis of 50 studies, showed that enhanced CI consistently provided more information that the standard police interview. Suggesting that it is worth using the enhanced version.