Coding, Capacity and Duration of Memory Flashcards
define short term memory STM:
- the limited capacity memory store
- coding is mainly acoustic (sounds)
-capacity between 5-9 items on average
-duration around 18 seconds
define long term memory LTM:
-permanent memory store
-coding mainly semantic (meaning)
-has unlimited capacity and
-can store memories for up to a lifetime
define coding:
-format in which information is stored in the various memory stores
- the process of converting info between different forms
define capacity:
amount of information that can be held in a memory store
define duration:
length of time information can be held in memory
what did Alan Baddeley (1966a, b) do?
Baddeley gave different lists of words to four groups of participants to remember
participants were shown the original words and were asked to recall them in correct order.
explain the types of word groups these were?
group 1 - acoustically SIMILAR - words sounding similar
group 2- acoustically DISSIMILAR- words that sounded different
group 3 - semantically SIMILAR- words with similar meanings
group 4- semantically DISSIMILAR- words with different meanings
what was the findings of this study?
recalling from STM, they tended to do worse with ACOUSTICALLY similar words
when they recalled the word list after a time interval of 20 mins, recalling LTM, they did WORSE with the semantically similar words
what do these findings suggest?
that info is coded acoustically in STM and semantically in LTM
Separate Memory Stores STRENGTH:
Baddeley’s study identified a clear difference between 2 memory stores
Later research shows that there are some exceptions of Baddeley’s findings
BUT the idea that STM uses mostly acoustic coding and LTM mostly semantic has stood the test of time
therefore what does this mean?
this was an important step to understand the memory system which led to the multi-store model
what is a LIMITATION of Baddeley’s study?
-study used quite artificial stimuli , rather than meaningful material
-e.g. word list had no personal meaning to participants SO the findings may not tell us much about different memory tasks (especially in everyday life)
-when processing more meaningful information, people may use semantic coding even for STM tasks
so what does this suggest?
the findings from this study have LIMITED APPLICATION
what did Joseph Jacobs 1887 study?
Capacity- found he measuring the digit span, he found what capacity is
explain the study?
- the researcher read out 4 digits , participant recalls out loud in correct order
- if correct, researcher reads out 5 digits and so on until participant cannot recall correct
- which indicates the digit span
what did Jacobs find?
that the mean span of digits across all participants was 9.3
mean span of letters was 7.3
what is a strength of Jacobs study?
it can be easily replicated
although some of the participants digits spans may have been underestimated because they were distracted (confounding variables),
Jacobs studies have been confirmed by other better controlled studies since - Bopp and Verhaegen
suggests that his study was a valid test of digit span in STM
Span of memory chunking - George Miller 1956:
Miller made an observation on everyday practice
he noted that things come in 7s
he thought that the span (capacity) of STM was around 7 items
he noted that people can recall 5 words easily as they can recall 5 letters
- this is done by chunking, grouping sets of digits or letters into units or chunks
LIMITATION Miller ?
Miller may have overestimated STM capacity
- Nelson Cowan 2001 reviewed other research and concluded that the capacity of the STM is only around 4 chunks
this suggests that the lower end of Miller’s estimates (5 items) is more appropriate than 7 times
Duration of STM : Margaret and Lloyd Peterson 1959
tested 24 students in 8 trials (each trial = one test)
on each trial, student given a consonant syllable to remember and a three digit number
student counted back from this number until told to stop (stopped any mental rehearsal of the consonant syllable , increasing duration of the STM for the syllable)
on each trial they were told to stop after periods of 3,6,9,12,15,18 secs , retention interval
what were the findings?
after 3 secs - average recalls was around 80% , after 18 seconds 3%, unless we repeat the information over
the findings suggest that the STM duration may be about 18 seconds unless we repeat the information over and over VERBAL REHEARSAL
LIMITATION - the Peterson’s study?
Meaningless stimuli in STM study:
-the study is not fully irrelevant as sometimes we try an remember meaningless information
- but recalling consonant syllables does not reflect most everyday memory activities where we try and remember meaningful things
so study lacks external validity
Harry Bahrick 1975 study? Duration of LTM
392 American participants aged between 17 and 74
high school yearbooks from participants + from schools
recall testing included photo recognition , free recall
what was the findings?
participants tested within 15 years of graduating were 90% accurate in photo recognition
after 48 years, recall declined to around 70% for photo recognition
free recall less accurate than recognition -60% after 15 years and drops to 30% after 48 years
shows that LTM may last up to a lifetime for some material
