Coding, Capacity and Duration Flashcards
Baddeley’s (1966) research on coding - Method
Coding, Capacity & Duration
Gave different lists of words to 4 groups.
Group 1 - acoustically similar
Group 2 - acoustically dissimilar
Group 3 - semantically similar
Group 4 - semantically dissimilar
Ppts shown og words and asked to recall in correct order.
Baddeley’s (1966) research on coding - Findings
Coding, Capacity & Duration
When they recalled from STM, they did worse on acoustically similar. When they recalled from LTM, they did worse on semantically similar.
Info in STM - coded acoustically
Info in LTM - coded semantically
Strength of Baddeley (1966)
Coding, Capacity & Duration
Identified clear difference between two mem stores.
Later research showed there are execptions to Baddeley’s findings. But idea that STM is mostly acoustic and LTM mostly semantic has stood test of time.
Important step in our understanding of mem system, led to MSM
Limitation of Baddeley (1966)
Coding, Capacity & Duration
Used artifical stimuli.
Word lists had no personal meaning to ppts. Baddeley’s findings may not tell us much about coding in diff kinds of mem tasks. When processing more meaningful info, people may use semantic coding for STM & vice versa.
Therefore, findings from study have limited application.
Jacob’s (1887) research on digit span
Coding, Capacity & Duration
Researcher read 4 digits and ppt recalled them out loud in correct order. If this correct, researcher read 5 digits and so on. Jacob’s found that mean digit span was 9.3 and mean for letter span was 7.3.
Strength of Jacob’s (1887) research on digit span
Coding, Capacity & Duration
Has been replicated.
Study is very old and lacked adequate controls (confounding variables). Despite this, Jacob’s findings have been confirmed by newer studies (Bopp and Verhaeghen, 2005).
Suggests Jacob’s study is a vaild test of digit span in STM
Miller’s (1956) research on capacity and chunking
Coding, Capacity & Duration
Miller made observations of everyday practise.
Noted that things come in sevens (days of week, deadly sins, etc)
Thought capacity of STM was 7 chunks, plus or minus 2.
Noted that people recalled 5 words as easily as 5 letters - chunking
Limitation of Miller’s (1956) research on capacity and chunking
Coding, Capacity & Duration
Miller overestimated STM cap.
Cowan (2001) concluded that cap of STM is only about 4 chunks (plus or minus 1).
Suggests that lower end of Miller’s estimate is more appropiate that 7
Peterson x2 (1959) duration of STM research
Coding, Capacity & Duration
24 students in 8 trials
On each trial, ppt given consonant syllable (e.g. YCG) & 3-digit number to count back from (prevents mental rehearsal)
Each trial last for varying time periods (3, 6, 9 ,12 ,15 & 18s)
After 3s, recall was 80%
After 18s, recall was 3%
Peterson x2’s findings suggested that STM duration is about 18s w/o verbal/mental rehearsal
Peterson x2 Evaluation
Coding, Capacity & Duration
Limit: stimulus material was artificial
Study is not completely irrevelant as we do sometimes try to remember fairly meaningless material
Even so, recalling consonant syllables doesn’t reflect most everday memory activities
There4, study lacks external validity
Bahrick et al (1975) duration of LTM research
Coding, Capacity & Duration
392 USA ppts aged between 17 & 74 tested on recall of their yearbooks
Recall tested in 2 ways - photo-recognition test consisting on 50 photos or free recall where ppts recalled all names of graduating class
Photo recog - w/in 15 years of grad, 90% accurate / after 48 years, 70%
Free recall - after 15 years, 60& accurate / after 48 years, 30%
Shows LTM may last up to a lifetime for some material
Bahrick et al (1975) Evaluation
Coding, Capacity & Duration
Strength - high external validity
Researchers investigated meaningful memories
When studies of LTM were conducted w/ meaningless pictures, recall rates were lower (Shepard, 1967)
There4, Bahrick et al’s findings reflect more ‘real’ estimate of duration of LTM
