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