Models Of Memory Flashcards
What is the multi store model of memory?
This was first described by Richard Atkinson and Richard Shiffrin (1968)
Atkinson and Shiffrin argue that our memory involves a flow of information through a series of stages in a fixed linear sequence. There are three unitary stores and each store has its own coding, capacity and duration.
1) Sensory register
2) Short term Memory or STM
3) Long term Memory or LTM
Accordingly, the MSM can be described as an information processing model (like a computer) with an input, process and output.
Describe the multi store model of memory
First, information is detected from the environment by the sense organs and enters the sensory register (SR).
The coding for the sensory register depends on the sense so can be haptic, iconic, echoic, gustatory or olfactory. Because the SR takes in information from all the senses, this explains why its capacity is unlimited. However, the duration of the SR is very short – around 250 milliseconds otherwise it decays.
If attention is payed to this information in the SR then it enters the short term memory (STM).
Information from the STM is transferred to the long-term memory only if that information is rehearsed. Rehearsal was initially described by Atkinson and Shiffrin as maintenance rehearsal, but Shiffrin later suggested that rehearsal could be elaborative (Raaijmakers, & Shiffrin, 2003).
The STM has a limited capacity (5-9 items) and duration (between 18 - 30 seconds). Information will decay from the STM within 30 seconds maximum unless maintenance rehearsal occurs. Prolonged rehearsal will move information into the LTM.
The LTM is a permanent memory store. This means it has an unlimited capacity, a lifetime duration although coding in the LTM is mainly semantic. When we want to recall information stored in the LTM it must be transferred back into the STM through a process called retrieval.
If rehearsal does not occur, then information is forgotten, lost from short term memory through the processes of displacement or decay.
Maintenance Rehearsal is when we mentally repeat the material – this is how material transfers from the STM to the LTM
Elaborate Rehearsal is based on when we give the material some kind of meaning and is a more advanced type of rehearsal – Atkinson and Shiffrin did not really mention this type of rehearsal when they introduced the Multi-Store Model.
What does the sensory register do?
Stores sensory information from the environment for a short period of time. Atkinson and Shiffrin (1968) proposed that there are five separate sensory stores to accommodate different kinds of sensory information:-
• Iconic store is where visual images are kept for a short period.
• Echoic store is where auditory senses are kept for a short period.
• Haptic store in sensory memory retains physical senses of touch and internal muscle tensions.
• Gustatory store is related to taste information
• Olfactory store is related to smell
What is the duration capacity and coding of the sensory register?
Duration: very brief, less than half a second (250 milliseconds)
Capacity: unlimited
Coding: depends on the sense- visual, auditory, taste, smell, touch.
The sensory store is constantly receiving information from your senses but most of this receives no attention and decays within less than a second. If you pay attention to the information it moves into the STM.
Describe the study that shows evidence for the sensory register
Sperling (1960)
Method – in a lab experiment, pps were shown a grid with three rows of four letters for 50 milliseconds (0.05 seconds). They then had to immediately recall either the whole grid, or a randomly chosen row indicated by a tone (high, medium or low) played straight after the grid was shown
What are results and conclusion of Sperling study
Results- When pps were asked to recall a particular row, pps could recall on average, 3 out of 4 items, no matter which row had been selected.
Conclusion – the pps didn’t know which row was going to be selected, but still managed to recall 3 out of the 4 letters in each row suggesting that almost the whole grid was held in their sensory register showing that the capacity is very large but the duration is very short
Evaluate Sperling study
Because this was a lab experiment, it was highly scientific. The variables would be controlled, and it would be easy for someone to replicate the study. However, the artificial setting of the study means it lacks ecological validity – people don’t normally have to recall letters in response to a sound, so the results might not represent what would happen in the real world.
Strength of the multi store model of memory
1) One strength of the MSM is that it can explain primacy and recency effects
It was argued that we are more likely to remember words at the beginning of a list because they are the first words we see, and we have enough time to rehearse them. This increases the likelihood that they will move into the LTM. This is called the primacy effect
It is also argued that we are more likely to remember words from the end of the list as they are still held in our STM. This is called the recency effect.
Research evidence for this comes from Murdoch’s study who found that when pps were given lists of words to learn ranging from 10 -40 words, and they were asked to free recall these words. Murdoch found the serial position effect – in other words he found that pps tended to remember the words depending on their position in the list. He therefore found that pps recalled the first few words in the list and the last word but not the words in the middle of the listThe reason for this was the primacy and recency effect. In other words we remember words from the beginning of a list as they have gone into our LTM (since we have rehearsed them) – primacy effect and words at the end of the list because they are still in our STM – recency effect whereas the words in the middle of the list had been there too long to be held in short term memory (STM) (due to displacement) and not long enough to be put into long term memory (LTM). This is referred as a asymptote.
In a nutshell, when participants remember primary and recent information, it is thought that they are recalling information from two separate stores (STM and LTM).
2) Another strength of the MSM is that case studies support the idea that STM and LTM are separate stores.
H.M was a patient studied by Scoville and Milner (1957). His brain damage was caused by an operation to remove the hippocampus from both sides of his brain to reduce the severe epilepsy he had suffered. After the operation, HM’s personality and intellect remained intact and he could still recall a list of 6 numbers in order. This shows H.M’s short term memory was still intact, but his surgery had left him unable to form new long term memories. Thus HM’s case shows that if you can lose one type of memory but not the other they must be separate as the MSM argues.
3) Brain-scanning techniques have also supported the idea that long and short term memories are separate stores.
Beardsley (1977) used brain scanning to investigate brain activity and found that the different parts of the brain are active during STM and LTM tasks – for example, the prefrontal cortex was active during STM but not LTM tasks. Squire et al. (1992) also used brain scanning and found the hippocampus was active when LTM was engaged. This suggests that the STM and LTM are separate stores as was shown in the brain scans. However there is still an ongoing debate about which brain areas are active during STM tasks and LTM tasks and research suggests that the hippocampus may be responsible for transferring STM information into the LTM!
Weakness of the multi store model of memory
One weakness of the MSM is the idea that all information needs to be rehearsed in order to move in the LTM is an over simplification as MSM does not explain flashbulb memories.
It doesn’t take into account that information more relevant to our lives is far easier to remember. Similarly if we do not fully understand a piece of information no matter how many times we rehearse it is unlikely it will stay in our LTM for a long period of time.
Craik and Watkins argued that there are two types of rehearsal- maintenance and elaborative. Maintenance rehearsal just means repeating things, and is normally only sufficient for keeping information in short term memory. The MSM only focuses on this type of rehearsal. However, the other type of rehearsal - elaborative rehearsal (linking information to existing knowledge and processing it on a deeper level) is generally required to form LTMs. Thus the MSM does not acknowledge that there are deeper levels of rehearsal and only focuses on one type.
Furthermore, in some cases, we don’t need to rehearse information at all to form LTMs for example, Kulik and Brown found highly emotional, significant or shocking events (‘flashbulb memories’) are easily stored in our long term memories without any rehearsal. This suggests that the MSM simplifies the process by which we form LTMs.
2) Another weakness of the MSM is the evidence that suggests that the STM and LTM are not single stores.
It is now believed that STM can be divided up into at least 2 stores: one for visual information and another for auditory information. In support patient K.F sustained brain damage from a motorbike accident which left him with a severely impaired STM for verbal information only (his visual STM showed no impairment). This suggests that K.F had damaged just part of his STM and therefore that it is not a unitary store as the MSM argued. The working memory model is a far better explanation of this case study.
Evidence also suggests that LTM is not a single store as described by the MSM. Amnesic patients typically have damaged episodic memories, but intact procedural and semantic memories showing clearly that LTM must have more than one store.
3) A final weakness of the MSM is that most studies supporting the MSM lack ecological validity
In most supporting studies participants asked to complete simple, unrealistic tasks, which didn’t test their memories in ways relatable to everyday life .e.g. random lists of words, digits, trigrams. In real life we tend to form memories related to meaningful information. This suggests that the MSM lacks external validity because supporting evidence may not reflect how the memory works in real life.
