Zusammenfassung der Ressource
Coding, Capacity and Duration
- Coding
- Baddeley gave different lists of
words to four groups of
participants to remember
- Group 1:
Acoustically similar
- STM found hard to recall in order
- Suggests we code
acoustically in STM
- Group 2: Acoustically
dissimilar
- Group 3: Semantically
similar
- LTM found hard to
recall after 20 minutes
- Suggests we code
semantically in LTM
- Group 4: Semantically
dissimilar
- Has separate memory stores which is
a strength and helps with the
understanding of MSM
- A limitation is that it used
artifiial stimuli rather than
meaningful material
- Capacity
- Joseph Jacobs measured digit span in 1887
- He would read out a digit order
containing 4 digits then add one each
time they got the sequence correct
- Mean span for digits was 9.3 items and
the mean span for letters was 7.3
- Although it is very old, it weas
replicated and his findings were
confirmed by Bopp and Verhaeghen in
2005
- George Miller (1956) realised that most
things come in sevens (7 days, 7 notes on
music scale, 7 deadly sins)
- Miller's Magic Number = 7-+2
- Supports Jacobs initial findings
- Also noted we could remember 5
words as easy as 5 letters and we do
this by chunking (grouping sets of
digits/letters together)
- He may have overestimated the STM capacity as
Cowan (2001) reviewed other research and
concluded that the capacity is around 4+-1
- Duration
- Peterson and Peterson tested 24 students in 8 trials
- Student given consonant syllable to
remember (such LRW)
- Also given 3-digit number and
the student counted back in
threes until told to stop (299, 296, 293 etc)
- Stopped at 3,6,9,12,15,18 seconds
to ask for consonant syllable
(retention interval)
- After 3 seconds, average recall =
80% and after 18 seconds
average recall = 3%
- Peterson and Peterson decided that the STM was
about 18 seconds unless we repeat the info
multiple times (verbal rehearsal)
- The stimulus material was artificial as it was nonsensical syllables
but we do try remember meaningless material such as phone
numbers but it does not reflect day-to-day behaviour which means
the study lacked external validity
- Harry Bahrick et al (1975) studied
392 American participants
between ages 17 and 74
- Tested in photo-recognition
- 90% after 15 years
- 70% after 48 years
- Tested in free recall
- 60% in 15 after 15 years
- 30% after 48 years
- This shows that the LTM may last up to a lifetime for some material
- It has high external validity as researchers have investigated
meaningful memories and when studies on LTM were
conducted with meaningless pictures the recall rates were
lower which suggests Bahrick's findings reflect a more 'real'
estimate of the duration of LTM