coding, capacity & duration

• • Duration refers to the amount of time that information can be stored in each memory store. The duration of STM is 18-30 seconds, as demonstrated by Petersen et al (1959), who found that increasing retention intervals decreased the accuracy of recall of consonant syllables in 24 undergraduates, when counting down from a 3 digit number (preventing mental rehearsal).
• • Capacity refers to the volume of information/data which can be kept in any memory store at any one time. For example, the capacity of STM is thought to be 7 +/- 2 items (Miller), whilst the capacity of LTM is unlimited.
• • Coding is acoustic in short-term memory, and semantic in long-term memory, as demonstrated by Baddeley (1966), who found that more mistakes are made when recalling acoustically-similar words straight after learning them (recall from STM), whilst more mistakes are made when recalling semantically-similar words 20 minutes after learning them (LTM recall).
• capacity research - Jacobs - digit span test - Participants were read digits starting with 4, if they could recall these correctly it increased to 5 etc - found a mean digit span of 9.3 and a mean letter span of 7.3
• duration research - Peterson and Peterson (STM) - found that increasing intervals between encoding and recall if consonant syllables decreased the recall accuracy - participants counted backwards from 100 to prevent rehearsal - average 80% recall after 3 seconds and 3% recall after 18 seconds
• duration research - Barhick (LTM) - studied photo recognition of yearbook pictures - 15 years after graduation recognition was 90% accurate and 48 years after graduation recall was 30% - shows some information can last a lifetime in LTM