Coding, capacity and duration of memory Flashcards
what is short-term memory (STM)
the limited capacity memory store, coding is mainly acoustic, capacity is between 5-9 items on average, duration is about 18 seconds
what is long-term memory (LTM)
the permanent memory store, coding is mainly semantic, unlimited capacity and duration of up to a lifetime
what is coding
the format in which information is stored in the various memory stores
what is capacity
the amount of information that can be held in a memory store
what is duration
the length of time information can be held in memory
describe research on coding
Baddeley (1966) gave different lists of words to participants to remember
group 1 - acoustically similar words
group 2 - acoustically dissimilar words
group 3 - semantically similar words
group 4 - semantically dissimilar words
participants were shown the original words and asked to recall them 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 from LTM, they did worse with semantically similar words
this suggests info is coded acoustically in STM and semantically in LTM
how is there separate memory stores (strength)
Baddeley indefinites a clear difference between two memory stores
idea that STM is mostly acoustic coding and LTM is mostly semantic coding stood the test of time
this lead to the multi-store model of memory
how is there artificial stimuli in Baddeley’s study (limitation)
the word lists had no personal meaning to participants, so his findings may not tell us much about coding in different kinds of memory tasks, especially in everyday life
more meaningful info may use semantic coding even for STM tasks
suggests limited application
describe research on digit span (capacity)
Jacobs (1887) - researcher read out four digits and the participants recalls these out loud in the correct order, if this is correct the researcher reads out five digits and so on until the participant cannot recall the order correctly
found the mean span for digits was 9.3 items, mean span for letters was 7.3
how has Jacob’s study been replicated (strength)
although Jacob’s study is very dated, which may have lacked adequate controls to monitor cofounding variables, his findings have been confirmed by later, better controlled studies (Bopp and Verhaeghen 2005)
suggests Jacob’s study is a valid test of digit span in STM
describe research on span of memory and chunking (capacity)
Miller (1956) noted that things come in sevens, e.g., seven notes on the music scale, seven days of the week, etc
he thought that the capacity of the STM is about 7 items, + or - 2
also noted that people can recall five words as easily as five letters
this is done through chunking - grouping sets of digits or letters into chunks
how did Miller overestimate STM capacity (limitation)
Cowan (2001) reviewed other research and concluded that the capacity of STM is only about 4 + or - 1 chunks
this suggests that the lower end of Miller’s estimate is more appropriate
describe research on duration of STM
Peterson and Peterson (1959) tested 24 students in 8 trials each
on each trial, the student was given a consonant syllable to remember (e.g., YCG) and a 3-digit number to count backwards from until told to stop (to prevent any mental rehearsal of the consonant syllable)
on each trial they were told to stop after varying periods of time: 3-18 seconds (retention interval)
average recall was about 80% after 3 seconds, 3% after 18 seconds
suggests STM duration may be about 18 seconds
how was the stimuli meaningless in Peterson and Peterson’s study (limitation)
recalling consonant syllables does not reflect most everyday memory activities where what we are trying to remember is meaningful
this means the study lacked external validity
describe research on duration of LTM
Bahrick et al. (1975) studied 392 american participants aged 17-74
recall was tested on high school years books in various ways, including, photo-recognition or free recall of names
participants tested within 15yrs of graduation were about 90% accurate in photo recognition, 70% after 48yrs
free recall was 60% accurate after 15yrs, 30% after 48yrs
this shows LTM may last up to a lifetime for some material
