Coding, capacity and duration of the STM and LTM

coding

format in which info is stored in various memory stores

Alan Baddeley’s coding research - procedure

4 lists of words for ppts to remember - acoustically similar, acoustically dissimilar, semantically similar, semantically dissimilar, asked to recall in right order immediately then after 20min

Alan Baddeley’s coding research - results

immediate recall (short term memory) - ppts did worse with acoustically similar words, recall after 20 min (long term memory) - ppts did worse with semantically similar words

how is info coded in the STM

acoustically (by sound)

how is info coded in the LTM

semantically (by meaning)

capacity

how much info can be held in a memory store at one time

Joseph Jacobs capacity research

used digit span to measure capacity - reads list of 4 words and if recalled accurately then read 5 words, mean span for digits was 9.3, mean span for letters was 7.3

George Miller capacity research

observed everyday practice and noted things come in sevens so stm capacity is 7, also noted people can recall 5 items as easily as can recall 5 letters via chunking

duration

length of time info can be held in memory

Margaret & Peterson STM duration research - procedure

tested 24 students over 8 trials, in each trial given 1 consonant syllable and 1 3 digit no to remember, student counted backwards from number until told to stop to prevent rehearsal of syllables, on each trial told to stop after varying periods of time e.g. 3s, 6s, 9s, 12s (retention interval)

Margaret & Peterson STM duration research - results

after 3s avg recall was 80%, after 18s avg recall was 3%

Bahrick LTM duration research - procedure

studied 392 american ppts between age 17-74, high school yearbooks obtained from ppts and schools, recall tested with photo recognition test with 50 photos and free recall test where recalled all names in graduating class

Bahrick LTM duration research - results

ppts tested within 15 years of graduation were 90% accurate in photo recognition but declined to 70% after 48 years, free recall less accurate than photo recognition, 60% after 15 years and 30% after 48 years

duration of STM

18s without rehearsal

duration of LTM

may last for up to a lifetime for some material