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Coding, capacity & duration
Research on coding:
Coding = The way info is transferred into a form that can be stored
Baddeley (1966): gave di erent word lists to 4 groups of ppts to remember:
• Group 1 & 2 = acoustically similar. E.g cat, can, cab & acoustically dissimilar. E.g great, large, big
• Group 3 & 4 = semantically similar. E.g large, big & semantically dissimilar. E.g good, hot
Found: ppts found that their immediate recall was worse for accoustically similar words as STM codes acoustically. After 20 mins -
ppts worse at recalling semantically similar words as LTM codes semantically
Research on capacity:
Capacity = the amount of info the memory store holds
1) Digit span - Jacobs (1887):
• researcher gives number of digits to recall in correct order out loud - if correct then they add more digits to recall - go until ppt
cant recall them correctly - nal number = digit span
• Found: mean span for digits across all ppts was 9.3 numbers and 7.3 letters
2) span of memory & chunking: miller (1956):
• Observed everyday practice. He noted things that came in 7’s like 7 notes on musical scale, 7 days of week, 7 deadly sins etc
• He suggested that the span/capacity of STM is 7+/-2 items - but it is increased by chunking (grouping sets of digit or letters
into meaningful units or chunks)
Research on duration:
Duration = the length of time that the memory store holds info
1) Duration of STM: Peterson & Peterson (1959) =
• 24 psych students given consonant syllable. E.g YCG to recall after di erent intervals of time. E.g 3, 6, 9, 12, 15 or 18 seconds
- during time intervals ppts had to count backwards from a 3 digit number
• Found: as time intervals increased, correct recall decreased - after 3 seconds correct recall was 80%, after 18 seconds correct
recall was about 3% - suggests that our STM has a duration of up to 18 seconds without rehearsal
2) Duration of LTM: Bahrick et al (1975) =
• 392 American ppts aged between 17 and 74 - their recall of yearbook photos was tested by: 1) photo-recognition test - 50
photos from high school yearbooks. 2) free recall test - ppts had to list names of their graduating class
• Found: recognition test was 90% accurate after 15 years, and 70% after 48 years. Free recall test had 60% recall after 15
+ Bahrick et al (duration) - study used real life memories - — Baddeley (coding) & Peterson and Peterson (duration)
tested memories from meaningful things - high ecological - arti cial tasks as it used meaningless words/stimuli - it
validity - his ndings re ect a more “real estimate of the may not generalise to real world memory tasks - lacks
duration of LTM ecological validity
— miller (capacity) - may overestimate STM capacity -
later research found that STM capacity was about 4+/-1
chunk - suggests that the lower end of millers estimate is
more appropriate than 7 items
fi fi fl ff fi ff
Coding, capacity & duration
Research on coding:
Coding = The way info is transferred into a form that can be stored
Baddeley (1966): gave di erent word lists to 4 groups of ppts to remember:
• Group 1 & 2 = acoustically similar. E.g cat, can, cab & acoustically dissimilar. E.g great, large, big
• Group 3 & 4 = semantically similar. E.g large, big & semantically dissimilar. E.g good, hot
Found: ppts found that their immediate recall was worse for accoustically similar words as STM codes acoustically. After 20 mins -
ppts worse at recalling semantically similar words as LTM codes semantically
Research on capacity:
Capacity = the amount of info the memory store holds
1) Digit span - Jacobs (1887):
• researcher gives number of digits to recall in correct order out loud - if correct then they add more digits to recall - go until ppt
cant recall them correctly - nal number = digit span
• Found: mean span for digits across all ppts was 9.3 numbers and 7.3 letters
2) span of memory & chunking: miller (1956):
• Observed everyday practice. He noted things that came in 7’s like 7 notes on musical scale, 7 days of week, 7 deadly sins etc
• He suggested that the span/capacity of STM is 7+/-2 items - but it is increased by chunking (grouping sets of digit or letters
into meaningful units or chunks)
Research on duration:
Duration = the length of time that the memory store holds info
1) Duration of STM: Peterson & Peterson (1959) =
• 24 psych students given consonant syllable. E.g YCG to recall after di erent intervals of time. E.g 3, 6, 9, 12, 15 or 18 seconds
- during time intervals ppts had to count backwards from a 3 digit number
• Found: as time intervals increased, correct recall decreased - after 3 seconds correct recall was 80%, after 18 seconds correct
recall was about 3% - suggests that our STM has a duration of up to 18 seconds without rehearsal
2) Duration of LTM: Bahrick et al (1975) =
• 392 American ppts aged between 17 and 74 - their recall of yearbook photos was tested by: 1) photo-recognition test - 50
photos from high school yearbooks. 2) free recall test - ppts had to list names of their graduating class
• Found: recognition test was 90% accurate after 15 years, and 70% after 48 years. Free recall test had 60% recall after 15
+ Bahrick et al (duration) - study used real life memories - — Baddeley (coding) & Peterson and Peterson (duration)
tested memories from meaningful things - high ecological - arti cial tasks as it used meaningless words/stimuli - it
validity - his ndings re ect a more “real estimate of the may not generalise to real world memory tasks - lacks
duration of LTM ecological validity
— miller (capacity) - may overestimate STM capacity -
later research found that STM capacity was about 4+/-1
chunk - suggests that the lower end of millers estimate is
more appropriate than 7 items
fi fi fl ff fi ff
