Short and long term memory

• STM

  Capacity - 7±2 items

  Duration - short duration / less than 18 seconds

  Coding - STM largely encoded acoustically
• LTM

  Capacity - infinite capacity

  Duration - Forever

  Coding - LTM largely encoded semantically
• CAPACITY = how much data can be held in a memory store
• -Capacity can be assessed using digit span (letters/numbers) - Jacobs found digit span was 9.3 for items and 7.3 for letters - Miller argues digit span is said to be 7+/-2 ‘chunks of information
• DURATION = how long a memory lasts before it is no longer available
• STM: - Peterson and Peterson ( 1959) - Used 24 students tested over 8 trials - On each trial a participant was given a consonant syllable and a 3- digit number (THX 512) - They were asked to recall the consonant syllable after a retention interval of 3,6,9,12,15 or 18 secs. • Participants were 90% correct after 3 secs, 20% correct after 9 secs and only 2% correct after 18 secs—supports the idea that STM has a short duration ( less than 18 secs)
• LTM: - Bahrick et al. (1975) tested 400 people of various ages (17-74) on their memory of their classmates. 2 types of test were used. - A photo-recognition test (of 50 photos) and free-recall • Photo recognition 90% accuracy after 15 years, after 48 years this declined to 70% • Free recall 60% after 15 years, 30% after 48 years
• ENCODING = the way information is changed so that it can be stored in memory
• Acoustic similarity


  Words that sound similar but have different meanings
• Acoustically similar but semantically dissimilar words


  • cat
  • cab
  • can
  • cad
  • mad
  • max
  • mat
  • man
• Semantic similarity


  Words that have similar meanings but sound different
• Semantically similar but acoustically different words


  • great
  • large
  • big
  • huge
• Baddeley (1966a and 1966b)


  Used word lists to test the effects of acoustic and semantic similarity on STM and LTM
• Participants had difficulty remembering semantically similar words in STM but not in LTM
• Acoustically similar words posed little problem for STMs but led to muddled LTMs
• Short-term memory (STM)


  Largely encoded acoustically
• Long-term memory (LTM)


  Largely encoded semantically