capacity, coding and duration Flashcards
describe the capacity of the STM
Joseph Jacobs (1887)
assessed the capacity using digit span
he found that the average span for digits was 9.3 items and 7.3 for letters
George Miller (1956) the magic number 7+-2 (5-9 items)
what are some evaluation points for the capacity of the STM?
- the capacity of the STM may be more limited
Cowen (2001) reviewed a variety of studies on the capacity of STM and said it was likely to be limited to four chunks. This suggests that the capacity isn’t as extensive as predicted and that Millers lower end of the magic number is more valid.
-the size of the chunks matters.
the size of the chunks influences how many you can remember. Simon (1974) found people had a shorter memory span for larger chunks.
-the capacity of the STM is also reliant on individual differences. Jacobs also found that recall (digit span) increased with age. 8-year-olds remembered on average 6.6 digits, however, 19-year-olds could remember on average 8.6 digits. this suggests brain capacity increases with age or people develop strategies to remember things as they get older.
describe the duration of the STM
Peterson and Peterson (1959)
24 students tested over 8 trials. participants were each given a consonant syllable and three-digit number (e.g THX 512). they were asked to recall the consonant syllable after retention intervals of 3,6,9,12,15 or 18 seconds. during the retention interval, they had to count down backwards from their three-digit number.
participants on average were 90% correct over 3 seconds, 20% correct after 9 seconds, and only 2% correct after 18 seconds.
this suggests that STM has a very short duration of 3-18 seconds.
describe the duration of the LTM
Bahrik (1975)
tested 400 people of various ages from 17-48 on their memory of their classmates. a photo recognition test consisted of 50 photos from the participant’s school yearbook. in a free-recall test, participants were asked to list the names they could remember.
participants tested within 15 years of graduation were about 90% accurate in identifying faces. after 48 years of graduation, this declined to about 70% for photo recognition. Free recall was about 60% accurate after 15 years, dropping to 30% after 48 years.
what are some evaluation points for the duration of STM?
-testing STM was artificial.
trying to memorise consonant syllables does not truly reflect most everyday memory activities where we are trying to remember meaningful things.
-STM results may be due to displacement.
In Petersons study, participants were counting the numbers in their STM which could displace or ‘overwrite’ the syllable to be remembered. Reitman (1974) used auditory tones instead of numbers so that this displacement couldn’t occur.
describe coding in the STM and LTM
information can be stored acoustically, visually and semantically.
acoustically similar words: cat, cab, can, cad
semantically similar: great, large, big, huge
Baddeley (1966) used words to test the effects of acoustic and semantic similarity on STM and LTM. he found people had greater difficulty remembering acoustically similar words in STM but not LTM whereas semantically similar words posed no problem for the STM but led to muddled LTM.
suggesting the STM is largely encoded acoustically whereas LTM is largely encoded semantically.
evaluation of coding for STM and LTM
- Baddeley may not have tested LTM
for STM the participants were asked to recall words immediately but for LTM, the participants were asked to recall words after 20 mins. it is questionable as to whether its a real test of the LTM.
-STM may not exclusively be acoustic and LTM may not exclusively be semantic.
some experiments such as Brandimote’s have shown that information is also stored visually. Similarly, research such as Frost’s evidence shows that information is stored visually as well as semantically.
