STM

• Who researched short term memory - coding?

  Baddeley
• What's Miller's magic number?

  7 +/- 2
• STM capacity can be improved by rhythmic grouping
• The duration of STM is 18 seconds
• What was duration of STM procedures?

  1. tested 24 students in 8 trials each
  2. in each trial participant given a trigram and a 3 digit number
  3. Student counted backwards from a number in 3s until told to stop after varying periods of time (3,6,9,12,15 seconds)
  4. student then had to recall trigram
• After 3 seconds, average recall in STM was 80%
• After 18 seconds, average recall in STM was 3%
• STM has a duration of 18 seconds
• Peterson and Peterson study on duration is easy to replicate as it's clear and can get consistent results, repeatable and reliable
• Peterson and Peterson strength

  Lab experiment

  no rehearsal so tests STM as high level of control

  High internal validity
• Duration of STM weakness:

  Repeated measure

  measures fatigue so not testing STM

  Not externally valid

  Too controlled and doesn't happen everyday
• Baddeley's aim was to investigate the effects of acoustic and semantic encoding in STM
• Baddeley divided participants into 4 groups and each group heard a list of 5 words from a category
• One of Baddeley's categories in his procedures is acoustically similar words (man, mad, map)
• One of Baddeley's categories in his procedures is acoustically dissimilar words (pen, day, few)
• One of Baddeley's categories in his procedures is semantically similar words (great, big, large)
• One of Baddeley's categories in his procedures is semantically dissimilar words (hot, old, late)
• Immediately after hearing the 5 words in Baddeley's study the participants were asked to recall them in the correct order
• Baddeley found that acoustically similar words were much harder to recall in the correct order than words with dissimilar sounds
• Baddeley found that similarity of meaning had a slight detrimental effect
• Baddeley found that the effects of similar sounds disappeared when he tested participants long-term learning suggesting that a major factor affecting encoding is whether the items are being stored in the STM or LTM
• Strength of Baddeley's study on STM

  research evidence supporting

  Conrad found that STM relies on sound of word and Participants had difficulty recalling acoustically similar words

  Reliable as results consistent over time
• Weakness of Baddeley's study on STM

  Mundane realism

  Participants wouldn't normally have been given this task to do so may have forgotten on purpose, lab experiment

  low external validity and demand characteristics
• multi store model of memory

  
• the STM has a duration of 18-30 seconds without rehearsal
• Study on capacity was calling out 4 digits, participant recalled them in the correct order, if they were correct the researcher reads out 5 digits and so on until the participants recall wrong
• Research found that the mean span for digits across all participants was 9.3 items and 7.3 for letters in the capacity of STM
• Limitation of capacity:

  Miller overestimated chunks, it was found by other researchers to be 4 +/- 1, so his use of 5 is better