Memory - encoding in STM and LTM
encoding - the way the information is saved.
STM (Short term memory)
Conrad (64) experiment - Visually presented students with a sequence of letters then asked the students to write down how many the could remember afterwards, he then showed them another sequence of letters and found students did worse remembering these as these were acoustically similar(rhyming) and letters that are acoustically dissimilar (non-rhyming) where easier to remember. Encoding mainly acoustic even though they where presented visually.
LTM (Long Term Memory)
Baddeley (66) - he presented lists of 10 short words, one at a time, some lists were semantically similar and others not. The Ps where tested immediately and then after 20 minute delay. After 20 minutes, Ps did poorly on the semantically similar words.
Suggests that we encode LTMs according to what they mean, Semantic - we get similar-meaning things confused.
Memory - Capacity Of STM & LTM
STM (Short Term Memory)
Miller (1956) - "the magic number 7 plus or minus 2". He proposed that people could remember chunks of information between 5 and 9. Results show that this is correct, as on average most people could remember between 5 and 9 bits of information. According to Miller, chunking (breaking it down into small pieces of information) increases the capacity of the STM.
Displacement - Capacity is limited, if information entering is quicker than it can be transferred to the LTM, either new items wont be able to enter or that the new items will push the older ones out. Waugh & Normal (1975) items are lost on a 'first-in-first-out' basis. Their experiment showed that when Ps trying to recall items, they were less likely to be able to do so if it was near the beginning.
LTM (Long Term Memory)
We haven't found a limit to the capacity so it is said to be of unlimited capacity.
Memory - Duration in the STM
STM (Short Term Memory)
Peterson and Peterson (1959) believed that information was help for about 20 seconds, if it was not rehearsed (maintenance), it faded.
They carried out a lab experiment. Ps were presented with sets of trigrams. They were then asked to recall in order after a delay of 3, 6, 9, 12, 15, 18 seconds. During the delay, Ps were asked a distraction task to prevent rehearsal (count backward by 3 - the Brown-Peterson technique)
Findings - The percentage recall was:
After 3 seconds: 80%
After 6 seconds: 50%
After 18 seconds: less than 10%
The longer the delay and distraction the less they could recall. Also suggesting that information could only be held for about 20 seconds.
Memory - Duration in the LTM
LTM (Long Term Memory)
Duration in the LTM could last anything up to a life time - from minutes to years.
It is difficult to test exact duration but Bahrick et al. (1975) tested US graduates.
He shown the graduates both photos and just names from their past classmates.
90% of Ps could remember faces and their names even 34 years after graduation, but after 48 years, it started to decline, especially for faces.
Memory - supporting the Multi-store Model
Glanzer and Cunitz (1966)
They read out words to Ps and asked them to recall as many as they can remember. They found out that the Ps could recall more from the start and the end of the list. These are the primary and recency effects.
Primary effect - the first words that had been heard, they had been able to rehearse them and then recall them from their LTM
Recency Effect - the words that had most recently been heard, can recall them as they are still in their STM.
This shows that there are two different stores (LTM & STM) and shows that elabritive and maintenance rehearsal is needed.
Memory - Criticisms of the Multi-Store Model
experience shows us that rehearsal is not needed for everyday life situations e.g. we remember a birthday party without rehearsing it.Must be another way for memories to enter your LTM.
Its unlikely that the stores in the memory are only unitary. Clive Wearing maintained some memories but not all. He lost all of his episodic long term memories (about events in his life) but kept some of his semantic memory (loving his wife). This suggests that it is unlikely there is only one store for LTM.
Memory - Description of the MSM
The MSM consists of 3 main stores; sensory memory, STM & LTM (in this order) Proposed by Atkinson and Shiffrin (1968). The environmental stimuli first enters the SM.
The sm is mostly encoded by haptic (physical senses of touch and internal muscle tensions), ionic (visual images) and echoic (auditory senses). Its capacity is around 4 to 10 seconds. Its duration is only less than 2 seconds. This was Proposed by Sperling (1960)
Attention moves the information along to the STM, its then encoded mainly acoustically, even though the items were presented visually. Its capacity is '7 plus or minus 2' - Miller (1956) who suggested people could remember chunks of information between 5 and 9. The information is stored in the STM for about 20 seconds, if not rehearsed, it fades.
Maintenance rehearsal - essential to keep the information in the STM. Elabritive rehearsal is needed for information to enter the LTM from the STM.
In the LTM. Atkinson and Shiffrin (1968) proposed that it was encoded by semantic meaning (similar things). its duration is infinite, can remember everything till the end of your life. It has unlimited capacity, remember as much as you want, although you can't stop remembering information. You recall information from your LTM to your STM by retrieval.
Memory - Strengths and Weaknesses of the MSM
- It was the first model – so it stimulated further research e.g. Baddeley & Hitch WM
- Lots of supporting evidence of distinct stores for SM, STM and LTM – different encoding, duration & capacity.
- It was supported by the Glanzer & Cunitz (1966) ‘Serial Position Effect’ - which showed that LTM and STM are separate, and also suggested simple rehearsal is important
- Supporting case studies
- Supporting brain imaging evidence
- New evidence memory stores are unlikely to be unitary: amnesiacs and Working Memory model (WMM)
- Memory is unlikely to be passive – decision making etc.
- Memory is unlikely to always be linear – evidence: brain damaged patient
- Simple rehearsal can’t be all - evidence: everyday life show it’s what we do with information, not just how many times we do it, is also important
Memory - Eye Witness Testimony (EWT)
EWT is a legal term. It is an account provided by a person of an event that they have witnessed. It includes things such as the identification of the perpetrators, details of the crime scene etc. EWT is an important part of research in human memory.
Memory - Strengths of the WMM
- much more plausible than the MSM as if explains STM in terms of both temp. storage and active processing
- attempts to explain how memory actually functions. Evidence has been presented that suggests the phonological loop plays a key role in the development of reading and is not operative in some children with dyslexia. It helps us comprehend complex text and learn new spoken vocab.
- Physiological evidence exsits using studies involving brain scans. PET scans have shown that differennt areas of the brain are used while undertaking verbal and visual tasks. These may correspond to components of the WMM
- WMM doesn't overemphasis the importance of rehearsal in STM. It is just one option in the articulatory loop instead of being the only means of transferring info to the LT store.
- research support comes from dual-task studies, although such studies are rather artificial however patients like KF could remember visual but not verbal stimuli in STM so much be at least two systems in STM.
- Extremely influential model and more psychologists use it in preference to the STM.
Memory - Weaknesses of the WMM
- WMM doesn't explain changes in processing ability that occur as a result of practice or time
- Capacity of the Central Executive has never been measured
- It isn't clear how the Central Executive works or what it does. This vagueness means that it can be used to explain almost any experimental result
- WMM only concerns itself with STM and is not a comprehensive model of memory
Memory - Description of the WMM
The WMM includes the 'Central Executive' which controls everything. It has limited capacity and it determines how resources are allocated, directs attention to tasks, sets task goals and retrieves processes from the LTM. Bunge et al (2000) used FMRI (Functional Magnetic Resonance Imaging) scans. When Ps were doing dual tasks, the FMRI scans showed a lot more activity. Increased attentional demands of the two simultaneous tasks increased brain activity. Provides support for proposed role of the Central Executive.
The Episodic Buffer was added in 2000 because the MSM needed a more general store. It is a 'slave system' and deals with specific types of info. It is an extra storage system but limited capacity. It integrates info from all other areas.
The phonological Loop, which consists of the auditory store (inner ear) which is a temporary storage system, holds verbal information in a speech based form. It has limited capacity by recorded length (2 seconds) and the articulatory control process (inner voice) which is also a temporary storage system and has limited capacity. words can be maintained by subvocal repetition and it is concerned with speech production. Baddeley & Hitch (1976) support this with their dual task technique (the use of the same component). Ps repeated a phrase over and over again while trying to read, their concurrent verbalization was low due to articulatory suppression.
Memory - Description of the WMM continued.
Baddeley (1996) shows that when the both use the central executive resources, perfomance was worse. This shows that the central executive can only control one store
Visuo-spatial Sketchpad visuo means visual (what things look like) and spatial, relationships between things. Also known as the inner eye. Sheped & Feng (1972) gaves Ps a net of a cube with two arrows on then asked them "Imagine folding a net into a cube - will the two arrows meet?". This study suggests that visual images work in a very similar way to real-life perception.
Memory - Loftus & Palmer's Study on EWT (Exp. 1)
- 45 Ps were shown short video clips
- they were split into 5 groups, 9 Ps in each one
- All of the Ps were asked 'about how fast were the cars going when they ____ each other?'
- Each group was given a different verb to fill in the blank. These were 'smashed, collided, bumped hit or contacted'
This was a laboratory experiment and was done to investigate how information provided to a witness after an event will influence their memory of that event.
Smashed - 40.8mph, Collided - 39.3mph, Bumped - 38.1mph, Hit - 34.0mp, Contacted - 31.8mph
misleading information in a question can influence the participants memory of an event.
Memory - Loftus & Palmer Study on EWT (exp. 2)
150 Ps were shown a short film that showed a multi-vehicle car accident and then tehy were asked questions about it. the Ps were split into 3 groups (50 in each). Group one was asked 'How fast were the cars going when they hit each other?'. Group two was asked 'How fast were the cars going when they smashed into each other?'. Group three wasn't asked about the speed. One week later all Ps were asked 'Did you see any broken glass?' There was no broken glass.
The aim was to see if misleading information could influence the memory of an event.
Group one - 7 people saw broken glass but 34 didn't. Group two - 16 people saw broken glass but 43 didn't. Group 3 - 6 people saw broken glass but 44 didn't.
The results show that the verb used in the original question influenced whether the Ps thought they had seen broken glass.
Memory - Strengths and Weaknesses of Loftus & Palm
- it was a laboratory experiment therefore there is more control over external variables (more repectablity)
- No serious ethical issues
- It was an experiment so there was a cause and effect. We can conclude it was the changed verb that caused the inaccuracies.
- It avoids any characteristics.
- Less mundane realism
- less ecological validity
- Some ethical issues, the video may be upsetting
- biased sample - all Ps were western (ethnocentric)
- All students (same age)
- Experiment 1 was a small sample size.
Memory - Weapon Focus Effect
Loftus et al (1987) wanted to know if the presence of a weapon can affect the accuracy of a recall.
Experiment - Ps where put in different situations 1) A man comes out holding a pan or 2) a man comes out holding a bloody knife. They were then asked to identify the two different men. People could identify the man holding the pen better as the attention was focused more on the knife and not the other man.
Advantages - Mundane realism, it was an experiment therefore can use cause and effect
Disadvantages - Ethical issues, they had been lied to and it was a traumatic experience.
Memory - Age
Poole and Lindsay (2001) - how misleading suggestions from parents influence childrens testimony. 3-8 year olds were enganged in a science demonstration, parents read a story with true and false descriptions of what happened. Children were asked where about they had got the information (source monitoring). Some older children could carry out the tast, younger children couldn't.
This shows that there are important implication of small children's testimony since they seem very poor at source monitoring.
Yarmey (1993) - found a difference in confidence of recall. Asked a young women to stop people in the street and chat to them for 15 seconds. Did this with 651 Ps of varying age. 2 minutes later the Ps were stopped and asked to recall the physical characteristics of the women. All age groups performed similary but younger age groups were significantly more confident in their recall.
This shows that all age groups perform similary but younger age groups are more confident in recall.
Memory - Age Continued
Memon et al. (2003) - worked with two age groups (6-33) and (60-82). When they were questions 35 minutes after anevent, age had little effect on accuracy of recall, however, a week later the older age group had declined significantly in their accuracy.
This shows that when the delay is short, there was no difference in the accuracy of the two groups, but when it was delayed by one week, the older group were not s accurate.