- Created by: Daisy Essex
- Created on: 27-03-19 15:06
Coding, Capacity and Duration
Coding - Converting information from one form to another
Coding is acoustic in short-term memory, and semantic in long-term memory, as demonstrated by Baddeley (1966), who found that more mistakes are made when recalling acoustically-similar words straight after learning them, whilst more mistakes are made when recalling semantically-similar words 20 minutes after learning them.
Capacity - The amount of information that can be held in a memory store.
The capacity of STM is thought to be 7 +/- 2 items, whilst the capacity of LTM is unlimited. This is based on Miller’s idea that things come in groups of 7 (e.g. 7 days of the week). ‘Chunking’, grouping sets of digits or letters into units or chunks, can help us recall information.
Duration - The length of time information can be held in memory store.
The duration of STM is 18-30 seconds, as demonstrated by Petersen et al (1959), who found that increasing retention intervals decreased the accuracy of recall of consonant syllables when counting down from a 3 digit number (preventing mental rehearsal). The duration of LTM is unlimited, as shown by Bahrick et al (1975).
Evaluation of Coding, Capacity and Duration
- Coding research uses artificial stimuli
Baddeley's study used lists of words which had no personal meaning to the participants. This means it is hard to generalise to other memory tasks.
- Capacity research lacks validity
Jacobs's study was conducted a long time ago which means it may lack control. This means that there may have been confounding variables that weren't controlled.
- Duration uses meaningless stimuli
Peterson and Peterson's study used artificial material. Trying to memorise constant syllables does not reflect real-life memory activities. This means the study lacked external validity.
The multi-store model
Proposed by Atkinson and Shiffrin (1968)
Sensory register - receives and stores information from the environment through our senses. Two types of information: Iconic (sight) and Echoic (hearing). Its capacity is unlimited, the duration is tiny (250 milliseconds) and coding depends. Attention affects whether the stimulus goes further into the model.
Short term memory - holds all the information the individual is thinking about consciously at one time. Its capacity is 7+/- 2, the duration is 18- 30 seconds and information is coded acoustically. Maintenance rehearsal occurs when we repeat new information allowing it to stay in STM. Prolonged maintenance rehearsal allows information to pass into LTM whereas lack of rehearsal causes forgetting.
Long term memory - permanent memory store for information that has been rehearsed for a prolonged time. Its capacity is unlimited, the duration is potentially forever and is coded semantically. When we want to recall information, it has to be transferred back into STM by retrieval.
Evaluation of the multi-store model
+ Research evidence
Supported by research that shows STM and LTM differ. Baddeley found that we mix up words that sound similar when using STM but when using LTM we mix up words that have a similar meaning. This clearly shows that coding in STM is acoustic and in LTM it is semantic. This, therefore, means they are different and supports the MSM as the two stores are separate and independent.
- More than one STM
Shallice and Warrington (1970) study a patient with amnesia. They found his STM for digits was poor when the researchers read the digits out loud to him. But his recall was much better when he was able to read the digits himself. This research shows there must be an STM store to process visual information and another to process auditory information.
- Types of Rehearsal
The MSM states that what matters in rehearsal is the amount of it you do. However, Craik and Watkins (1973) found what really matters is the type of rehearsal. Maintenance rehearsal doesn't transfer information into LTM but instead remains in STM. Whereas, elaborative rehearsal is needed for long term storage. This occurs when we link information to your existing knowledge, so you think about what it means.
Types of long term memory
Tulving (1985) believed MSM of LTM is too simple. He believed there are three LTM stores.
Procedural: Memory of how we do things e.g. riding a bike. These memories require a lot of repetition and practise. We can recall these memories without conscious awareness or effort. We might find them hard to explain to someone.
Episodic: Personal memories of events e.g. last birthday or wedding. You remember when things happen e.g. last week or yesterday. The memory will include people, places, objects, and behaviours. You consciously recall the memories.
Semantic: Knowledge of the world e.g. like a dictionary. It contains knowledge of concepts e.g. animals, love, singers etc. It's less personal and we don't remember when we learnt the meanings. It contains an immense collection of material which is constantly being added to.
Evaluation of types of long term memory
HM and Clive Wearing had impaired episodic memory as a consequence of Amnesia. They had difficulty recalling events of their pasts. But their semantic memories weren't affected as they could still remember meanings of words and their procedural memories were also intact as they could remember how to perform simple tasks like tying their shoelace, walking and talking etc. This supports Tulving that there are different memory stores in LTM.
+ Brain scan evidence
Tulving got participants to do various memory tasks while connected to a PET scan. He found that episodic and semantic memories are recalled in the prefrontal cortex. The left hemisphere recalled semantic memories and the right hemisphere recalled episodic memories. This supports Tulving as there is a physical reality to the different types of LTM
- Maybe more types
Cohen and Squire (1980) disagree with Tulving. They accept procedural memories but argue that episodic and semantic memories are stored together in one LTM store called the declarative memory store i.e. consciously recalled memories. Procedural memories, therefore, are non-declarative.
The working memory model
The WMM was proposed by Baddeley and Hitch (1974) as a model of STM
Central executive: Monitors incoming data, makes decisions and allocates slave systems to tasks (controls them). It has a limited capacity and modality free coding.
Phonological loop (PL): Processes auditory information and preserves the order in which information arrives. It has a 2-second capacity and acoustic coding. It is subdivided into the phonological store, which stores verbal material temporarily, and the articulatory control system which allows maintenance rehearsal.
Visuospatial sketchpad: Processes and stores visual and spatial information. It consists of the visual cache which stores visual data and the inner scribe which records the arrangement of objects. Its capacity is 3/4 objects and codes visually.
Episodic buffer: Temporary store of information integrating the visual, spatial and verbal information processed by other stores. Its capacity is limited to about 4 chunks and codes modality free.
Evaluation of the working memory model
+ Duo-task performance
Baddeley (1975) showed that participants had more difficulty doing two visual tasks than doing a visual and verbal task at the same time. This is because both visual tasks compete for the same slave system whereas, when doing a verbal and visual task at the same time, there is no competition. This means there must be a separate slave system (VSS) that processes visual input.
- Central executive
Some psychologists argue the central executive doesn't explain everything. Baddeley (2003) said, "It's the most important but least understood component of WM". It needs to be more clearly specified than just being attention. For example, some psychologists believe it may consist of separate components, therefore, the WMM hasn't been fully explained.
+ Case study evidence
Shallice and Warrington (1970) had a patient, KF, who had suffered brain damage. KF had poor STM for verbal information but could process visual information. This suggests that just his phonological loop had been damaged, and the other areas of memory are intact. This supports the WMM however, evidence from brain-damaged patients may not be reliable as they are unique cases who have had traumatic experiences.
Interference explanation of forgetting
Interference occurs when two pieces of information conflict with each other resulting in forgetting one or both pieces of information.
Two types of interference:
1) Proactive - Older memories disrupt newer ones e.g. a teacher having difficulty remembering names in her current class because she has learnt many names in the past.
2) Retroactive - Newer memories disrupt older ones e.g. a teacher having difficulty remembering old students' names as she had learnt many new ones.
Similarities between memories cause interference to be harder (McGeoch & McDonald (1931))
Procedure: They studied retroactive interference by changing the amount of similarity between two sets of materials. Part. had to learn 10 words until they remembered all of them. They then learned a new list. There were six groups who learnt different lists: 1-synonyms, 2-antonyms, 3-unrelated original, 4-consonant syllables, 5-three-digit numbers, 6-no new list.
Findings: When the participants recalled the original list of words, their recall depended on the second list. The most similar material (synonyms) produced the worst recall. This shows interference is strongest when the memories are similar.
Evaluation of interference
+/- Evidence from lab studies
Many lab experiments have been carried out into forgetting e.g. McGeoch and McDonald's research. Most of these studies support interference and by using lab studies extraneous variables can be controlled meaning the studies can be replicated. However, lab studies use artificial materials, e.g. learning syllables, which are meaningless and don't represent everyday situations. This means the studies may lack generalisability and therefore have low external validity.
The part. do not have much motivation to remember stimuli used in the experiments whereas in real life they would have much more e.g. studying for exams. This means part. might be less accurate and make the effects of interference to appear stronger.
+ Real life studies
Baddeley & Hitch (1977) asked rugby players to remember the names of the teams they had played that season. Recall of the teams was dependent on how many teams they had played in the meantime. So, a player's recall of a team from three weeks ago was better if they had played no matches since.
Retrieval failure explanation of forgetting
Retrieval failure: When we don't have the necessary cues to access memory. The memory is available but not accessible unless a suitable cue is provided.
Encoding Specificity Principle (ESP): Tulving (1983) reviewed research into retrieval failure and found if a cue is present at encoding (learning) and retrieval we are more likely to remember it. If the cues at encoding and retrieval are different or absent at retrieval then we are less likely to forget it. Some cues are linked meaningfully e.g. STM makes me recall information about STM.
Context-dependent forgetting (external cues): Godden and Baddeley (1975) carried out a study on deep sea divers. Procedure: Divers learnt a list of words and were asked to recall the words afterwards. There were four conditions; learn on land-recall on land, learn on land-recall underwater, learn underwater-recall on land & learn underwater-recall underwater. Findings: Accurate recall was 40% lower in non-matching conditions. The external cues were different when learning and retrieval which led to retrieval failure.
State-dependent forgetting (internal cues): Carter and Cassaday (1998) gave hay fever tablets to participants which made them drowsy. They learnt a list of words and recalled them afterwards. There were four conditions; learn on drug-recall on drug, learn on drug-recall off drug, learn off drug-recall off drug & learn off drug-recall off drug. Findings: When the conditions differed, the performance on the memory tests were much worse. So when the cues are absent, then there is more forgetting.
Evaluation of retrieval failure
+ Research evidence
Godden and Baddeley & Carter and Cassaday are just two examples of retrieval of failure. Eysenck (2010) says retrieval failure is the main reason for forgetting in LTM. This evidence increases the validity of the explanation, especially in real life situations.
- Context effects
Baddeley (1997) argues context effects are not strong, especially in real life. Different contexts have to be very different before an effect is seen. For example, learning something in one room and recalling it in another is unlikely to result in much forgetting because the two contexts aren't different enough. This means that the real-life applications of retrieval failure due to contextual cues don't actually explain forgetting.
+ Research evidence for state-dependent forgetting
A study by Goodwin investigated the effect of alcohol on 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.
Misleading information affecting EWT
Leading question - A question that suggests a certain answer due to the way its phrased. Loftus and Palmer (1974) arranged participants to watch films of car accidents and answer questions about it. In the critical question, they were asked: "how fast were the cars going when they _ each other?" The verb changed for each group (5) from "hit" to "contacted" or "smashed". The verb smashed caused the speed of the car to have a mean of 40.5mph but the word contacted had a mean speed of 31.8mph. The leading question, therefore, affected eye witness testimony.
Response-bias explanation suggests leading questions have no effect on eyewitnesses' memories but do have an effect on their answers. Loftus and Palmer conducted a second experiment that supported the substitution explanation (leading questions change memory). This is supported as when the participant had the verb smashed, they were more likely to say they saw broken glass. This means the critical verb altered their memory.
Post-event discussion - when co-witnesses to a crime discuss it with each other causing the testimonies to be less accurate. Gobbert et al. (2003) studied participants in pairs where they watched a video of a crime but filmed from different points of view. They then discussed what they saw with each other before individually answering questions on recall. She found 71% of participants recalled aspects they didn't see but picked up from the discussion. In the control group, where there was no discussion, 0% recalled information they didn't see. Gobbert et al. concluded witnesses go along with each other for social approval or they believed another person is right - Memory conformity.
Evaluation of misleading information affecting EWT
+ Real life application
Loftus (1975) believes leading questions can have a distorting effect on memory so police officers need to be careful about how they word questions when interviewing eyewitnesses. This can improve lives by improving court trials to bring justice to victims.
- Artificial tasks
Loftus and Palmer used film clips which is very different from witnessing a real-life accident as clips lack stress and emotions which can influence memory. This is a limitation as artificial tasks can only tell us a little about how leading questions affect EWT in real accidents and crimes.
- Individual differences
Older people are less accurate than younger people when giving eyewitness reports. Anastasi & Rhodes (2006) found people aged 18-25 and 35-45 were more accurate than people aged 55-78. All age groups were more accurate when identifying people of their own age group (own age bias). Research studies in EWT use younger people which may mean some age groups appear less accurate.
(Demand characteristics - Zaragosa and McCloskey (1989) argue answers participants give in lab studies of EWT are results of demand characteristics as the participants want to please the researcher.)
Anxiety affecting eye witness testimony
Negative effect on recall
Anxiety creates psychological arousal which prevents us from paying attention to important cues, so recall is worse. Weapons cause anxiety so are useful when studying this. Johnson and Scott (1976) told participants they were taking part in a lab study. While they were waiting, they heard an argument in the next room. In the 'low-anxiety' condition, a man walked through the waiting area carrying a pen with greasy hands. In the 'high-anxiety' condition, they heard the same argument but heard breaking glass. A man walked out of the room holding a paper knife covered in blood. They then had to pick out the man from 50 photos. 49% of the low anxiety group was able to identify him whereas, in the high anxiety condition, 33% could identify him. Tunnel theory - witnesses' attention narrows to focus on the weapon because it's the source of anxiety.
Positive effect on recall
The fight or flight response is triggered which increases alertness and improves memory as we are more aware of cues. Yuille & Cutshall (1986) conducted a study of a real-life shooting in a gun shop in Canada. The shop owner shot a thief. There were 21 witnesses and 13 agreed to take part in the study. The interviews were held 4-5 months after the incident and were compared to police interviews at the time of the shooting. Accuracy was determined by the number of details reported. The witnesses were also asked to rate how stressed they were at the time of the incident and asked if they had any emotional problems since the event. They found witnesses were very accurate in their accounts and there was little change in the accuracy after 5 months. Those participants who reported the highest levels of stress were most accurate (88% compared to 75%). Yerkes-Dodson Law - Performance will increase with stress but only to a certain point.
Evaluation of anxiety affecting EWT
- Weapon focus due to surprise
The study by Johnson and Scott may test surprise rather than anxiety. The reason the participants focus on the weapon was that they were surprised to see it rather than because they were scared. Pickel (1998) conducted an experiment where someone was holding either scissors, a handgun, a wallet or a raw chicken in a salon video. Eyewitnesses' accuracy was much lower when the object was unusual e.g. the raw chicken. This suggests the weapon focus effect is due to unusualness rather than anxiety which therefore tells us nothing significant about EWT.
- Field studies may lack control
Researchers usually interview real-life eyewitnesses sometime after the event. Discussions with other people, accounts they have read or seen in media or the effects of being interviewed by the police all may have happened since the incident which could affect the recall of the eyewitness and therefore gives the researcher less control over the extraneous variables.
- Ethical issues and Yerkes-Dodson Law
Creating anxiety for participants may be risky as it can cause them psychological harm. This is why real-life studies are so beneficial. Also, anxiety is difficult to define and measure accurately as it has many elements e.g. cognitive, behavioural, emotional and physical. But the Yerkes-Dodson explanation assumes only one of these is linked to poor performance - physical arousal.
Cognitive interview for improving EWT
Fisher and Geiselman (1992) used four main techniques to improve EWT.
1) Report everything - Witnesses are encouraged to include every little detail of the event even though these details may seem irrelevant.
2) Reinstate the context - Trying to mentally recreate an image of the situation, including details of the environment such as weather conditions and the individual's emotional state including their feelings at the time of the incident. These details can then act as a trigger, to help the person recall more information
3) Recall in reverse order - The witnesses are asked to recall the scene in a different chronological order e.g. from the end to the beginning.
4) Recall from changed perspective - Trying to mentally recreate the situation from different points of view e.g. describing what another witness present would have seen.
Features of the enhanced cognitive interview are encouraging the witness to relax and speak slowly, offering comments to help clarify witness statements, asking open-ended questions and adapting questions to suit the understanding of the individual witnesses.
Evaluation of the cognitive interview
- More time consuming than standard police interview
More time is needed to establish a relationship with the witness and allow them to relax. CI also requires special training for police officers and many forces have not been able to provide time for this training. This means it is unlikely that the 'proper' version of the CI is actually used.
+ Research support
Kohnken et al reviewed research into eyewitness testimony and found that the cognitive interview increased the amount of correct information recalled by 48%, compared to the standard interview. Also, Stein & Memon found that the cognitive interview is effective because people remember more when given cues. They made Brazilian female cleaners watch a video of abduction and then used the cognitive interview & standard interview to gain eyewitness reports, finding those who were in the cognitive interview condition not only recalled more but were accurate in the information recalled.
- Lacking mundane realism
Previous research has found that anxiety affects recall of eyewitness testimony, so by using videos that the participants are not emotionally involved, the results lack ecological validity and are not easily generalised. The research may also have researcher bias, as the experimenter wants to find the cognitive interview more effective, so maybe giving greater clues when interviewing participants in this condition, affecting the reliability of these results.