Memory Flashcards
Coding
The format in which information is stored in the various memory stores
Capacity
The amount of information that can be held in a memory store
Duration
The length of time information can be held in memory
Short-term memory
The limited capacity memory store. Coding is mainly acoustic (sounds), capacity is 7+-2 items on average, duration is between about 18 and 30 seconds
Long-term memory
The permanent memory store. Coding is mainly semantic (meaning), it has unlimited capacity and can store memories for up to a lifetime
Research on coding
Alan baddeley
He gave different lists of words for groups of participants to remember:
group 1- acoustically similar
Group 2 – acoustically dissimilar
Group 3 -semantically similar
Group 4-semantically dissimilar
Participants were shown the original words and asked to recall them in the correct order. When they had to this recall task immediately after hearing it (STN Rico), they tended to do worse with acoustically similar words
If participants were asked to recall the words list after a time interval of 20 minutes (LTM recall), they did worse with the semantically similar words. This suggests that information is coded semantically in LTM
Acoustically similar
Words sounding similar
Cat cab can
Acoustically dissimilar
Words sounding different
Pit few cow
Semantically similar
Words with similar meaning
Great large big
Semantically dissimilar
Words that all had different meanings
Good huge hot
Research on capacity - digit span
How much information can STM hold at any one time, i.e. what is the capacity? Joseph Jacobs developed a technique to measure digit span. Researcher gives for example, four digits and then the participant is asked to recall it in the correct order out loud. If this is correct the researcher reads out 5 digits and so on until the participant cannot record the order correctly. This determines the individuals’ digit span
He found that the mean span for digits across all participants was 9.3 items. The main span for letters was 7.3
Research on capacity – span of memory and Chunking
George Miller made observations of everyday practice. For example, he noted that things come in sevens: there are seven notes on the musical scale, seven days of the week, seven deadly sins, and so on. This suggests that the span (or capacity of STM) is about seven items. However, Miller also noted that people can recall 5 words as well as they can recall five letters. They do this by chunking – bunching sets of digits or letters into units or chunks
Research on duration - STM
Margaret and Lloyd Peterson tested 24 undergraduate students
Each student took part in 8 trials. On each trial the student was given a consonant syllable (also called a trigram, such as YCG) to remember and was also given a 3 digit number
Student was then asked to found backwards from that 3 digit number until they were told to stop
The counting backwards was to prevent any mental rehearsal
On each trail they were told to stop after a different amount of time -3,6,9,12,15 or 18 seconds. This is called retention interval
Findings suggest that STM may have a very short duration, unless we repeat something over and over again
As retention interval (seconds) increased, % of correct responses decreased
Research on duration - LTM
Harry Bahrick studies 392 participants in Ohio aged 17 to 74
High school yearbooks were obtained. Recall was tested in various ways, including: 1. Photo recognition test consisting of 50 photos, some from the year book, 2. Free recall test where ps recalled all the names of their graduating class
Ps who were tested within 15 years of graduation were about 90% accurate in photo recognition. After 48 years, recall declined to about 70% for photo recognition
Free recall was less good than recognition. After 15 years this was about 60% accurate
This shows that LTM can last a long time
Baddeley research on coding evaluation
Artificial stimuli
One limitation of his study was that it used quite artificial stimuli rather than meaningful material
The word lists had no personal meaning to participants. This means we should be cautious about generalising the findings to different kinds of memory task. E.g. when processing more meaningful info, people may use semantic coding even for STM tasks.
This suggests that the findings from this study have limited application
Jacobs research on capacity - digit span evaluation
Lacking validity
One limitation of the study is that it was conducted a long time ago. Early research in psychology often lacked adequate control
E.g. some participants may have been distracted while they were being tested so they didn’t perform as well as they might
This would mean that the results might not be valid because there were confounding variables that weren’t controlled
However the results of this study have been confirmed in other research, supporting its validity
Millers research on capacity - span of memory and chunking evaluation
Not so many chunks
One limitation of his research is that he might have overestimated the capacity of STM
E.g. Cowan reviewed other research and concluded that the capacity of STM was only about 4 chunks
This suggests that the lower end of millers estimate (5 items) is more appropriate that 7 items
Peterson’s research on duration of STM evaluation
A limitation of the study is that the stimulus material was artificial. Trying to memorise consonant syllables does not reflect most real life memory activities where what we are trying to remember is meaningful. So we might say that this study lacked external validity
However, we do sometimes try to remember fairly meaningless things, such as phone numbers, so the study is not totally irrelevant
One explanation for why we forget things in STM is that the memory trace simply disappears if not rehearsed (spontaneous decay). An alternate explanation is that the info in STM is displaced- the STM has a limited capacity and any new info will push out what is currently there. In the Peterson study ps counted down during the retention interval
Bahricks Study on duration of LTM evaluation
Higher external validity
One strength of the study is that it has higher external validity. Real life meaningful memories were studied. When studies on LTM have been conducted with meaningless pictures to be remembered, recall rates were lower (e.g. Shepard)
The downside of such real life research is that confounding variables are not controlled, such as the fact that his participants may have looked at the yearbook photos in the past and rehearsed their memory over the years
Multi store model
A representation of how memory works in terms of three stores called sensory register, short-term memory and long term memory. It also describes how information is transferred from one store to another, how it is remembered and how it is stored
Sensory register
The memory stores for each of our five senses, such as vision (iconic store) and hearing (echoic store ). Coding in the iconic sensory register is visual and in the echoic sensory register it is acoustic. The capacity of sensory registers is huge (millions of receptors) and information last for a very short time (less than half a second)
The case of HM
HM underwent brain surgery to relieve his epilepsy. Unfortunately for him, the procedure used was in its infancy and not fully understood. Crucially, a part of his brain known as the hippocampus was removed from both sides of his brain. We now know this is to be the central to memory function. When his memory was assessed in 1955, he thought the year was 1953, and that he was 27 (was 31) years old. He had very little recall of the operation and he could not remember speaking to someone just an hour earlier
His LTM was tested over and over again but never improve with practice. He would read the same magazine repeatedly without remembering it. He couldn’t recall what he has eaten earlier the same day. However, despite all this, he performed well on tests of immediate memory span, a measure of STM
Evaluation of the MSM
Supporting research evidence There is more than one type of STM There is more than one type of rehearsal Artificial materials There is more than one type of LTM
Supporting research evidence of the MSM evaluation
A major strength of the MSM is that it is supported by research studies that show that STM and LTM or indeed qualitatively different. E.g. Baddeley found that we tend to mix up words that sound similar when we are using our STMs. But we mix up words that have similar meanings when we use our LTMs. The strength of the study is that it clearly shows the coding in STM is acoustic and in LTM it is semantic. So they are different and this supports the MSMs view that these two memory stores are separate and independent
Further support is given by all the studies of coding, capacity and duration
There is more than one type of STM evaluation of MSM
The MSM states that STM is a unitary store, in other words there is only one type of short-term memory. However, evidence from people suffering from a clinical condition called amnesia shows that this cannot be true. E.g. Shallice and Warrington studied a patient with amnesia known as KF. They found that his STM for digits was very poor when they read them out loud to him. But his recall was much better when he was able to read the digits to himself. Further studies of KF and other people with amnesia showed that there could even be another Short-term store for non-verbal sounds (such as noises)
The unitary STM is a limitation of the MSM because research shows that at the very least there must be one short-term store to process visual information and another one to process auditory information. The working memory model includes the separate stores
There is more than one type of rehearsal evaluation of MSM
According to the MSM, what matters in rehearsal is the amount of it that you do
So the more you rehearse some information, the more likely you are to transfer it to LTM and remember it for a long time
However Craik and Watkins found that this prediction is wrong
What really matters about rehearsal is the type. They discovered that there are two types of rehearsal. Maintenance rehearsal is the type described in the MSM, but this does not transfer information into LTM. It just maintains it in STM, hence the name
Elaborative rehearsal is needed for long-term storage. This occurs when you link the information to your existing knowledge, or you think about what it means
This is a very serious limitation of the MSM because it is another research finding that cannot be explained by the model
Artificial materials evaluation of MSM
In every day life we form memories related to all sorts of useful things – people’s faces, their names, facts and so on
But a lot of the research studies that provide support for the MSM use none of these materials. Instead they use digits, letters and sometimes words. They even use what are known as consonant syllables that have no meaning
There is more than one type of LTM evaluation of MSM
There’s a lot of research evidence the LTM, like STM, is not a unitary memory store
For example, we have one long-term store for our memories of facts about the world, and we have a different one for our memories of how to ride a bicycle.
Types of LTM
Episodic memory
Semantic memory
Procedural memory
Episodic memory
A LTM store for personal events
It includes memories of when the events occurred and of the people, objects, places and behaviours involved
Memories from this store have to be retrieved consciously and with effort
Episodic memories example
The breakfast you ate this morning
Semantic memory
A LTM store for our knowledge of the world
Includes facts and our knowledge of what words and concepts mean
These memories usually also need to be recalled deliberately
Semantic memories example
The taste of an orange
Procedural memory
LTM store for our knowledge of how to do things
Includes our memories of learned skills
We usually recall these memories without making a conscious or deliberate effort
Procedural memory example
Driving a car
Types of LTM evaluation points
Clinical evidence Neuroimaging evidence Real life applications Problems with clinical evidence 3 or 2 types of LTM
Clinical evidence evaluation of types of LTM
Case studies of HM and Clive Wearing
Episodic memory in both men was severely impaired as a consequence of amnesia. They had great difficulty recalling events that had happened to them in their pasts
But their semantic memories were relatively unaffected
E.g. they still understood the meaning of words
This evidence supports Tulving’s view that there are different memory stored in LTM
Neuroimaging evidence evaluation of types of LTM
There is evidence from brain scan studies that different types of memory is stored in different parts of the brain.
E.g. Tulving got their participants to perform various memory tasks while their brain was scanned using a PET scanner. They found the episodic and semantic memories were both recalled from an area of the brain that was the prefrontal cortex. This area is divided Into, one on each side of the brain. The left prefrontal cortex was involved in recalling semantic memories. Episodic memories were recalled from the right prefrontal cortex
The strength of this finding is that it supports the view that there is a physical reality to the different types of LTM within the brain. It has also been confirmed many times we need to research studies, further supporting the validity of this
Real life applications evaluation of types of LTM
Being able to identify different aspects of LTM allows psychologists to target certain kinds of memory in order to better peoples lives.
E.g. Belleville demonstrate that episodic memories could be improved in older people who had a mild cognitive impairment. The trained participants performed better on a test of episodic memory after training then a control group
Your episodic memory is a type of memory most often affected by mild cognitive impairment, which highlights the benefit of being able to distinguish between types of LTM – because it enables specific treatments to be developed
Problems with clinical evidence evaluation of types of LTM
Psychologists are very interested in studying people with brain injuries. People like Clive wearing and HM have provided a lot of useful information about what happens when memory is damaged. This has even helped research to understand how memory is supposed to work normally. But such clinical studies are not perfect. For instance there is a serious lack of control of all sorts of different variables in clinical studies
Three types of LTM or two? Evaluation of LTM
Cohen and Squire disagree with Tulving’s division of LTM into three types. They accept that procedural memories represent one type of LTM. But they argue that episodic and semantic memories are stored together in one LTM store that they called declarative memory i.e. memories can be consciously recalled. In contrast procedural memories are non-decorative
Working memory model
A representation of STM. It suggests that STM is a dynamic processor of different types of information using subunits coordinated by a central decision-making system
Central executive
The component of the WNM that coordinates the activities of the three subsystems in memory. It also allocates processing resources to those activities