Coding, capacity and duration of memory Flashcards
short term memory
the limited capacity memory store. In STM, coding is mainly acoustic, capacity is between 5 and 9 items on average, duration is about 10 seconds
long term memory
the permanent memory store. In LTM, coding is mainly semantic, it has unlimited capacity and can store memories for up to a lifetime
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 the memory
who researched into the coding of memory ?
Alan Baddeley
what were the four groups in Baddeley’s research ?
-group 1, acoustically similar (words sounding similar, e.g. cat, cab, can)
- group 2, acoustically dissimilar (words sounding different, e.g. pit, few, cow)
- group 3, semantically similar (words with similar meanings, e.g. great, large, big)
- group 4, semantically dissimilar (words with different meanings, e.g. good, huge, hot)
what was Baddeley’s procedure ?
- ppt were shown the original words and asked to recall in the correct order
- when they did this task immediately, recalling from STM, they tended to do worse with acoustically similar words
- when they recalled the word list after a time interval of 20 minutes, recalling from LTM, they did worse with the semantically similar words
who tested memory capacity with the digit span research ?
Joseph Jacobs
what was Jacob’s procedure ?
researcher reads out repeatedly digits until the ppt cannot recall the order correctly - indicates the individual’s digit span
what was Jacob’s findings ?
- the mean span for digits across all participants was 9.3 items
- the mean span for letters was 7.3
who tested memory capacity through observations ?
George Miller
what did George observe and find ?
- observed everyday things
- noticed things came in seven
- e.g. notes on a musical scale, days of the week, deadly sins
what was George’s conclusions ?
capacity of STM is 7 +/- 2
five words can be recalled as easily as five letters. this is chunking
who researched the duration of STM ?
Peterson and Peterson
what were Peterson and Peterson’s procedure ?
- 24 students in eight trials
- each trials students were given a consonant syllable
- also given a 3-digit number
- counted back from the 3 digit number until asked to stop
- each trial they stopped for varying periods of time, 3,6,9,12,15 or 18
what were Peterson and Peterson’s findings ?
- after 3 seconds, average recall was 80%
- after 18 seconds, average recall was 3%
- suggests STM duration is around 18 seconds, unless we rehearse
who researched the duration of LTM ?
Bahrick et al (1975)
what was Bahrick’s procedure ?
- 392 American participants ages between 17 and 74
- high school yearbooks obtained from the participants
- recall tested in carious ways;
1. photo recognition test consisting of 50 photos, some from participants’ high school yearbooks
2. free recall test where participants recalled the all the names of their graduating class
what were Bahrick’s findings ?
- participants tested within 15 years of graduation were about 90% correct in photo recognition
- after 48 years, recalldeclined to about 70%
- free recall was less accurate. 60% after 15 years, 30% after 48 years
what was Bahrick’s conclusion ?
shows that LTM may last up to a lifetime
strength - what does separate memory stores do for Baddeley’s study?
P: clear difference between two memory stores
E: later research showed that there are exceptions to Baddeley’s findings
E: but the idea that STM mostly semantic has stood the test of time
L: important step in our understanding of the memory system, led to the multi-tore memory model
limitation - what does artificial stimuli do to Baddeley’s study?
P: used artificial stimuli instead of meaningful material
E: had no personal meaning to participants so may not tell us much about coding in different kinds of memory tasks, especially everyday life
E: when processing more meaningful information, people may use semantic coding even for STM tasks
L: suggests that findings from this study have limited application - lack ecological validity
strength - what does validity do for Jacob’s study?
P: has been replicated- very
told and early research often lacks adequate controls
E: e.g. some participants’ digit spans may have been underestimated because they were distracted (confounding variables)
E: despite this, Jacobs’ findings have been confirmed by other, better controlled studies
L: temporal validity
limitation - what does overestimation do to Miller’s research?
P: may have overestimated STM capacity
E: Cowan reviewed other research and concluded that the capacity of STM is only about 4 +/- 1 chunks
E: suggests that the lower end of Miller’s estimate is more appropriate that 7 items
limitation - what does a meaningless stimuli do to Peterson & Peterson’s study?
P: material was artificial
E: not completely irrelevant because we do sometimes try to remember fairly meaningless material
E: even so, recalling consonant syllables does not reflect most everyday memory activities where we are trying to remember is meaningful
L: means the study lacked external validity
strength - what does high external validity do for Bahrick et al’s findings?
P: high external validity because the researchers investigated meaningful memories
E: when studies om LTM were conducted with meaningless pictures to be remembered, recall rates were lower
E: suggests that Bahrick et al’s findings reflect a more ‘real’ estimate of the duration of LTM
