Short And Long Term Memory Flashcards
What is long term memory?
Your memory for events that have happened
What’s the duration and capacity of LTM?
Last anywhere from 2 minutes to 100 years.
It potentially has unlimited duration and capacity
How is LTM coded?
Its coded semantically
What is short-term memory?
Your memory from immediate events.
How is STM measured?
Seconds and minutes, rather than hours and days
What’s the duration and capacity of STM?
Short duration - seconds, minutes
Limited capacity - 7+/-2
How is STM coded?
Tends to be coded acoustically
Why does STM need to be rehearsed?
They will disappear - short duration
What is capacity?
A measure of how much can be held in memory.
What can STM be referred to as?
The working memory
How is capacity represented?
It’s represented in terms of bits of information, such as number of digits.
What is coding?
The way information is changed so that it can be stored in memory (also encoding)
How does coding work?
Information enters the brain via the senses.
It is then stored in various forms, such as visual codes (like a picture), acoustic codes (sounds) or semantic codes (the meaning of the experience).
What is duration?
A measure of how long a memory lasts before it is no longer available.
What are the differences between STM and LTM?
Capacity - limited
Capacity - infinite
Duration - short
Duration - lasts forever
Coding - acoustically
Coding - semantically
How can the capacity of the STM be assessed?
Using digit span
What was a study to assess the capacity of STM?
Jacobs (1887) used digit span.
He found that the average span for digits was 9.3 items and 7.3 for letters.
Jacobs suggested that it may be easier to recall digits because there are only 9 compared to 26 letters.
What did Miller do?
Miller (1956) reviewed psychological research and concluded that the span of immediate memory is about 7 items - sometimes a bit more, sometimes a bit less.
He also found that people can recall 5 words as well as they can recall 5 letters - we chunk things together and can then remember more.
What are the evaluate points for capacity?
The capacity of STM may be even more limited
The size of the chunk matters
Individual differences
What is meant by the capacity of STM may be even more limited?
Cowan (2001) reviewed a variety of studies on the capacity of STM and concluded that STM is likely to be limited to about 4 chunks.
This suggests that STM may not be as extensive as was first thought.
Research on the capacity of STM for visual information (rather than verbal stimuli) also found that four items was about the limit (e.g. Vogel, 2001).
This means that the lower end of Miller’s range is more appropriate.
What is meant by the size of the chunk matters?
It seems that the size of the chunk affects how many chunks you can remember.
Simon (1974) found that people has a shorter memory span for larger chunks, such as 8-word phrases, than smaller chunks, such as 1-syllable words.
What is meant by individual differences?
The capacity of STM is not the same for everyone.
Jacobs also found that recall (digit span) increased steadily with age; 8 year olds could remember an average of 6.6 digits whereas the mean for 19 year olds was 8.6 digits.
This age increase might be due to a gradual increase in brain capacity, and/or it may be that people develop strategies to improve their digit span as they get older, such as chunking.
Who studied the duration of the STM?
Peterson and Peterson (1959)
What was Petersons study?
Used 24 students.
Each participant was tested over 8 trials.
On each trial a participant was given a consonant syllable and a three-digit number (e.g. THX 512).
They were asked to recall the consonant syllable after a retention of interval of 3,6,9,12,15 or 18 seconds.
During the retention interval they had to count backwards from their 3 digit number.
What did the Peterson’s find?
Participants on average were…
90% correct over 3 seconds.
20% correct after 9 seconds
2% correct after 18 second
This suggests that STM has a very short duration - less than 18 seconds - as long as verbal rehearsal is prevented.
Who studied the duration of LTM?
Bahrick (1975)
What was Bahricks study?
Tested 400 people of various ages (17-74) on their memory of classmates.
A photo-recognition test consisted of 50 photos, some from the participants high-school yearbook.
In a free-recall test participants were asked to list the names they could remember of those in their graduating class.
What were Bahricks findings?
Participants who were tested within 15 years of graduation were about 90% accurate in identifying faces.
After 48 years, this declined to about 70% for photo recognition
Free recall was about 60% accurate after 15 years, dropping to 30% after 48 years.
What were the evaluative points for duration?
Testing STM was artificial
STM results may be due to displacement
What is meant by testing STM was artificial?
Trying to memories 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 (post codes).
This means that the study does have some relevance to everyday life.
What is meant by results may be due to displacement?
In the Peterson’s study participants were counting the numbers in the 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 Peterson’s study was due to displacement rather than decay, and was not measuring the duration of STM.
Nairne (1999) found that items could be recalled after as long as 96 seconds.
How is information stored?
It has to be written in memory in some form - it’s described as a code in which it is held in the form of sounds (acoustic), images (visual) or meaning (semantic).
What words are acoustically similar but semantically different?
Cat, cab, can, cap, mad, max, mat, man, map
What words are semantically similar but acoustically different?
Great, large, big, huge, broad, long, tall, fat, wide, high
What did Baddeley do to assess coding?
1966a and 1966b
Used word lists like those above to test effects of acoustic and semantic similarity on STM and LTM.
What did Baddeley find?
He found that participants had difficulty remembering acoustically similar words in STM and LTM, whereas semantically similar words posed little problems for STMs bet led to muddled LTMs.
This suggests that STM is largely encoded acoustically whereas LTM is largely encoded semantically.
What are the evaluative points for coding?
Baddeley may not have tested LTM
STM may not be exclusively acoustic
LTM may not be exclusively semantic
What is meant by Baddeley may not have tested LTM?
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.
What is meant by STM may not be exclusively acoustic?
In general STM appears to rely on an acoustic code for storing information.
However, some experiments have shown that visual codes are also used in STM.
For example, Brandimote (1992) found that participants used visual coding in STM if they were given a visual task (pictures) and prevented from doing any verbal rehearsal in the retention interval (they had to say lalala) before performing a visual recall task.
Normally, we translate visual images into verbal codes in STM, but, as verbal rehearsal was prevented, participants used visual codes.
Other research has shown that STM sometimes uses a semantic code (Wickens, 1976).
What is meant by LTM may not be exclusively semantic?
In general LTM appears to be semantic but, as with STM, this may not be always true.
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 STM and LTM is not simply acoustic or semantic but can vary according to circumstances
