Coding, capacity and duration of memory Flashcards
What is short term memory?
Limited capacity memory store.
Mainly acoustic
Capacity between 5-9 items
Duration 18 seconds
What is long term memory?
Permanent memory store
Coding mainly semantic
Unlimited capacity
Stores memories for up to a lifetime
What is coding?
Format in which information is stored in the various memory stores
What was Baddeley’s study for coding?
Gave different lists of words to groups to remember.
Group 1 (acoustically similar) - words sounded similar (cat, cab, can)
Group 2 (acoustically dissimilar) - words sounded different.
Group 3 (semantically similar) - words with similar meanings
Group 4 (semantically dissimilar) - words with different meanings
What were Baddeley’s findings?
When task was immediately, recalling from short term memory.
Tended to do worse with acoustically similar words.
When recalled list after 20 minutes, recalling from long term memory.
Did worse with semantically similar words.
Suggests information is coded
Acoustically - Short term memory
Semantically - Long term memory
What is an evaluation for coding?
Separate memory stores
Baddeley’s study identified clear difference between two memory stores.
Later research showed that there are some expectations to Baddeley’s findings.
But idea that short term memory uses mostly acoustic coding and long term mostly semantic has stood the test of time.
Important step in our understanding of memory system, which led to the multi store model.
What is an evaluation for coding?
Artificial stimuli
Baddeley’s study was that it used quite artificial stimuli rather than meaningful material.
Eg. the word lists had no personal meaning to participants.
Findings may not tell us much about coding in different kinds of memory tasks, especially in everyday life.
When processing more meaningful information, people use semantic coding even for short term memory tasks
Suggesting findings from this study have limited application.
What is capacity?
The amount of information that can be held in a memory store.
What did Jacobs find about capacity?
Digit span test
Researcher read out loud a digit list
Participants had to recall list he had read out
If they recalled it 100% accurately researcher added on more digits to the list he recalled and so on
What did Jacobs find?
Mean span for numbers - 9.3
Means span for letters - 7.3
Capacity of short term memory is 7 +/- 2
What were Millers observations?
Observations of everyday practice.
Things come in 7s
Eg. 7 notes on music scale, 7 day week.
Span of short term memory 7 +/- 2
But also people can recall 5 words as easily as they can recall 5 letters.
What is Chunking?
Grouping sets of digits or letters into units or chunks
What is an evaluation for capacity?
A valid study
Jacobs’ study has been replicated.
Study is very old
Often lacked adequate controls.
Some participants digit spans might have been underestimated because they were distracted during testing (confounding variable)
Despite this, Jacobs findings have been confirmed by other, better controlled studies since (Bopp)
Suggesting Jacobs’ study is a valid test of digit span in short term memory.
What is an evaluation for capacity?
Not so many chunks
Millers research may have overestimated short term memory capacity.
Cowan
Reviewed other research and concluded that the capacity of short term memory is only about 4 chunks +/- 1 chunks
Suggesting that the lower end of miller’s estimate is more appropriate than seven items.
What is duration?
The length of time information can be held in memory.
What did Peterson’s study about duration of short term memory?
24 students in 8 trials each.
One child given constant syllable (YCG) to remember.
Also given three digit number.
Student counted backwards from this number until told to stop.
Counting backwards to prevent any mental rehearsal of the consonant syllable.
Each trial they were told to stop after varying periods of time: 3,6,9,12,15 or 18 seconds until wrong (retention interval).
What were Peterson and Petersons findings?
When distraction task was done for 3s average recall accuracy - 80%
When distraction task was done for 18s average recall accuracy - 3%
Duration of short term memory - between 18-30 seconds
What did Bahrick et al around duration of long term memory?
392 American participants 17-74 years
High school yearbooks were obtained from participants or directly from schools.
1 - photo recognition test consisting of 59 photos, some from participants high school year books
2 - Free recall test where participants recalled all the names of their graduating class.
What were the findings of Bahrick’s study?
Participants tested within 15 years of graduation were about 90% accurate in photo recognition.
After 48 years, recall declines to about 70% for photo recognitions.
Free recall was less accurate than recognition
60% - 15 years
30% - 48 years
Showing that long term memory may last up to a lifetime for some material.
What is an evaluation for duration?
Meaningless stimuli in short term study
Peterson and Petersons study
The stimulus material was artificial
Study not completely irrelevant because we do sometimes try to remember fairly meaningless material.
Recalling consonant syllables does not reflect most everyday memory activities where what we are trying to remember is meaningful.
Meaning study lacked external validity.
What is an evaluation for duration?
High external validity of Bahrick et al’s study
High external validity.
Resreachers investigated meaningful memories.
Shepard
When studies on long term memory were conducted with meaningless pictures to be remembers, recall rates were lower
Suggesting his findings reflect a more ‘real’ estimate of the duration of long term memory.
