duration

• How many American participants were involved in bahrick 1975

  392 American participants
• What is a strength of Bahrick's study regarding external validity?

  • High external validity (ecological validity- can be applied to other settings, so is relevant to real life)
  • Closer to real life than Peterson + Peterson 1959
• How long can information be held in Short-Term Memory?


  Up to about 30 seconds
• What happens to information in Short-Term Memory if it is rehearsed?


  It can transfer to Long-Term Memory
• How long can information remain in Long-Term Memory?


  Indefinitely
• Does rehearsal guarantee successful transfer to Long-Term Memory?


  No, rehearsal does not always ensure success
• peterson + peterson 1959

  • aim- to see if rehearsal was necessary to hold information in the short term memory store
• peterson + peterson 1959- procedure

  • given trigrams
  • immediately asked to count backwards in sets of 3 for intervals of 3,6,9,12,15,18
• why where participants asked to count backwards for peterson + peterson 1959 


  to prevent rehearsal
• findings of peterson + peterson 1959

  • 3seconds - 90% trigram recall
  • 18seconds - 3% trigram recall
  • >18 seconds - virtually all information forgotten
  • concluded that information can't be held in the short term memory store without rehearsal
  • STM duration is 18-30seconds
• what is displacement 


  when new information displaces or removes old information from the short term memory store
• peterson + peterson 1959 (criticisms)

  disadvantages:

  • lacks ecological validity (not reflected in other settings, meaning not reflected in real life) - this is as it is not a normal everyday task to memorise trigrams
  • lacks mundane realism (not realistic to real life, so harder to generalise) - because it was conducted in a controlled experimental setting (artificial)
  • may produce demand characteristics (conducting the experiment in a highly controlled environment allows participants to guess the aim)

  advantages:

  • highly controlled setting means it can be easily replicated
• what are trigrams 


  three letter constants with no meaning (eg HLG)
• why are trigrams used

  • so no meaning can be attached, and therefore can't be semantically encoded to the short term memory store
• why can't peterson and peterson 1959 results be generalised 


  the participants were university students, so not representative of whole population- meaning can't be generalised
• peterson and peterson, may show effect of displacement due to counting backwards. this means the conclusions have low internal validity
• Bahrick 1975

  • 392 american participants aged 17-74
  • took their highschool year books and asked the participants to recall people from their graduating class

  two types of tests were used:

  • photo recognition (50 photos, some from year book, then had to name people)
  • free recall (had to recall names without any visual prompts)
• results of bahricks study

  • within 15yrs graduation - 90% photo recognition, 60% free recall
  • after 48 years of graduation - 70% photo recognition, 30 free recall

  meaning that long term memory may last up to a lifetime for some material, and free recall was less accurate than photo recognition
• lab- high control, low external validity

  field- low control, high external validity
• disadvantages of bahricks study (1975)


  lack of control of extraneous variables- the participants may be friends still with people from high school, may have looked over book in the past week etc.
• lab studies- have poorer retention as they lack emotional attachment (eg peterson + peterson 1959)