Memory Flashcards
evaluation
Capacity
One criticism of the research investigating STM is that Miller’s original findings have not been replicated.
Cowan (2001) reviewed a variety of studies on the capacity of STM and concluded that STM is likely to be limited to about four chunks. Research on the capacity of STM for visual information (rather than verbal stimuli) also found that four items were about the limit (e.g. Vogel et al., 2001). This means that the lower end of Miller’s range is more appropriate (i.e. 7 - 2 which is 5). This suggests that STM may not be as extensive as was thought.
Capacity
It seems that 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 eight-word phrases, than smaller chunks, such as one-syllable words. This continues to support the view that STM has a limited capacity and refines our understanding
The capacity of STM is not the same for everyone.
Duration
Another criticism of research investigating STM is that it is artificial.
Trying to memorise consonant syllables does not truly reflect most everyday memory activities where what we are trying to remember is meaningful. However, we do sometimes try to remember fairly meaningless things, such as groups of numbers (phone numbers) or letters (postcodes). This means that, although the task was artificial, the study does have some relevance to everyday life
Duration
A criticism of the Petersons’ study is that it did not actually measure what it set out to measure.
In the Petersons’ study participants were counting the numbers in their STM and this may displace or ‘overwrite’ the syllables to be remembered. Reitman (1974) used auditory tones instead of numbers so that displacement wouldn’t occur (sounds don’t interfere with verbal rehearsal) and found that the duration of STM was longer.This suggests that forgetting in the Petersons’ study was due to displacement rather than decay
Coding
In general LTM appears to be semantic but not always.
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 coding in LTM. Therefore it seems that coding in LTM is not simply semantic but can vary according to circumstances
Coding
Baddeley’s methodology has been criticised.
In the study by Baddeley, STM was tested by asking participants to recall a word list immediately after hearing it. LTM was tested by waiting 20 minutes. It is questionable as to whether this is really testing LTM. This casts doubt on the validity of Baddeley’s research because he wasn’t testing LTM after all
MSM
Controlled lab studies on capacity, duration and coding (described on the previous spread) support the existence of a separate short-and long-term store, which is the basis of the MSM.
Studies using brain scanning techniques have also demonstrated that there is a difference between STM and LTM. For example, Beardsley (1997) found that the prefrontal cortex is active during STM but not LTM tasks. Squire et al. (1992) also used brain scanning and found the hippocampus is active when LTM is engaged. This evidence provides strong support for the MSM
MSM
Psychologists have also shown that different areas of the brain are involved in STM and LTM from their study of individuals with brain damage.
One case involved a man referred to as HM (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. HM’s personality and intellect remained intact but he could not form new LTMs, although he could remember things from before the surgery This provides support for the MSM’s notion of separate stores, as HM was unable to transfer information from his STM to LTM, but was able to retrieve information from before his surgery (i.e. from his LTM)
MSM
The MSM has been criticised for its emphasis on maintenance rehearsal. Craik and Lockhart (1972) suggested that enduring memories are created by the processing that you do, rather than through maintenance rehearsal Things that are processed more deeply are more memorable just because of the way they are processed Craik and Tulving (1975) gave participants a list of nouns (eg shark) and asked a question that Involved shallow or deep processing - asked whether a word was printed in capital letters (shallow processing) or asked whether the word fitted in a sentence (deep processing). The participants remembered more words in the task involving deep processing rather than shallow processing. This suggests that the process of rehearsal does not fully explain the process of creating long-term memories. Deep or elaborative processing is also a key part of the process.
WMM
The main reason for developing the WMM was to account for dual task performance, described on the facing page. Hitch and Baddeley (1976) supported the existence of the central executive in one such study.
Task 1 occupied the central executive (eg. participants were given a statement ‘B is followed by A’and shown two letters such as ‘AB’ and asked to say true or false). Task 2 either involved the articulatory loop (eg, asked to say ‘the the the’ repeatedly) or involved both the central executive and the articulatory loop (saying random digits). Task 1 was slower when Task 2 involved both the central executive and the articulatory loop.
This demonstrates the dual task performance effect and shows that the central executive is one of the components of working memory
WMM
Studies of individuals with brain damage also support the WMM. Shallice and Warrington (1970) studied a man called KF whose short-term forgetting of auditory information was much greater than that of visual stimuli, In addition his auditory problems were limited to verbal material such as letters and digits but not meaningful sounds (such as a phone ringing). Thus his brain damage seemed to be restricted to the phonological loop. Another patient, SC, had generally good learning abilities with the exception of being unable to learn word pairs that were presented out loud. This suggests damage to the phonological loop (Trojano and Grossi, 1995). Another patient, LH, who had been involved in a road accident, performed better on spatial tasks than those involving visual imagery (Farah et al, 1988).
This supports the idea of separate visual and spatial systems, as suggested by the WMM
WMM
Some psychologists feel the concept of the central executive is too vague and doesn’t really explain anything. All it appears to do is allocate resources and essentially be the same as ‘attention: Critics also feel that the notion of a single central executive is wrong and that there are probably several components. Eslinger and Damasio (1985) studied EVR, who had had a cerebral tumour removed. He performed well on tests requiring reasoning, which suggested that his central executive was intact. However, he had poor decision-making skills (he would spend hours trying to decide where to eat, for example), which suggests that in fact his central executive was not wholly intact.
In summary the account offered of the central executive is unsatisfactory because it is probably more complex than Baddeley and Hitch originally suggested
Types of LTM
The distinction made between the three kinds of LTM is supported by brain scan research.
Episodic memory is associated with the hippocampus and other parts of the temporal lobe where the hippocampus is located, as well as with activity in the frontal lobe. Semantic memory also relies on the temporal lobe. Procedural memory activation is associated with the cerebellum, which is involved in the control of fine motor skills as well as the motor cortex. The basal ganglia and limbic system are also involved in this kind of learning.
Brain scans therefore indicate that the three types of memory are found in different parts of the brain Evidence from case studies offers further support for different types of LTM.
Types of LTM
The case study of HM was described on page 47. We noted that his ability to form new LTMs was affected by the destruction of his hippocampus (parts of his temporal lobes were also destroyed) but he retained his pre-existing LTMs. In fact this is a bit of a simplification. After the surgery, HM could still form new procedural memories but not episodic or semantic memories. For example, he was able to learn how to draw a figure by looking at its reflection in a mirror, a skill called mirror- drawing (Corkin, 2002). This is a procedural memory. However, he had no memory that he had learned this (an episodic/semantic memory).This supports the distinction between procedural and declarative memories, and hence the existence of multiple types of LTMand so are separate
Types of LTM
It is difficult to reach a firm conclusion by studying brain-damaged patients.
Problems with evidence from brain-damaged patients were considered on page 49 and they apply here too. In addition, the difficulty with studies of amnesiacs, including HM, is that it is difficult to be certain of the exact parts of the brain that have been affected until a patient has died. Most studies are conducted with living patients. Damage to a particular area of the brain does not necessarily mean that area is responsible for a particular behaviour - it may be acting as a relay station. Malfunction of the relay station would impair performance.
This means we cannot establish a causal relationship between a particular brain region and type of LTM.
