Coding, capacity, duration of memory

• procedure of baddeley: coding in STM and LTM

  acoustically similar words or dissimilar

  semantically similar words of dissimilar
• findings and conclusions of baddeley: coding in STM and LTM

  immediate recall worse with acoustically similar words, STM is acoustic.

  recall after 20 minutes worse with semantically similar words, LTM is semantic.
• procedure of jacobs: capacity of STM

  digit span: researcher reads four digits and increases until the participant cannot recall the order correctly.
• findings and conclusions of jacobs: capacity of STM

  on average, participants could repeat back 9.3 numbers and 7.3 letters in the correct order immediately after they were presented.
• procedure of miller: capacity of STM

  miller made observations of everyday practice. for example, he noted that things come in sevens: 7 notes on the musical scale, 7 days of the week, 7 deadly sins and so on.
• findings and conclusions of miller: capacity of STM

  the span of STM is about 7 items (plus or minus 2) but can be improved by chunking- grouping sets of digits/letters into meaningful units.
• procedure of Peterson and Peterson: duration of STM

  24 students given a consonant syllable to remember and a 3-digit number to count backwards for 3, 6, 9, 12, 15 or 18.
• findings and conclusions of Peterson and Peterson: duration of STM

  students recalled (on average) about 80% of the syllables correctly with a 3-second interval. average recall after 18 seconds fell to about 3%. suggesting that duration of STM without rehearsal is about 18 to 30 seconds.
• procedure of bahrick et al.: duration of LTM

  participants were 392 Americans ages between 17 and 74

  1. recognition test: 50 photos from participants' high school yearbook.
  2. free recall test: participants listed names of their graduating class.
• findings and conclusions of bahrick et al.: duration of STM

  participants tested 48 years after graduation were about 70% accurate in photo recognition. free recall was less accurate.
• limitation of baddeleys study: didn't use meaningful material

  the words used in the study had no personal meaning to the participants. when processing more meaningful information, people may use semantic coding even for STM tasks. this means the results of this study have limited application. we should be cautious about generalising the findings to different kinds of memory task.
• limitation of jacobs' study: conducted a long time ago

  early research in psychology often lacked adequate control of extraneous variables. for example, some participants may have been distracted while they were being tested so they didn't perform as well as they might. this would mean that the results may not be valid because there were confounding variables that were not controlled. however, these results have been confirmed in other research, supporting its validity.
• limitation of miller: overestimated capacity of STM

  for example, Cowan reviewed other research. he concluded that the capacity of STM was only about 4 chunks. this suggests that the lower end of Miller's estimate (5 items) is more appropriate than 7 items.
• limitation of Peterson and Peterson: artificial stimulus

  trying to memorise consonant syllables does not reflect most real-life memory activities where what we try to remember is meaningful. so it could be argued that this study lacked external validity. on the other hand, we do sometimes try to remember fairly meaningless things, such as phone numbers. so the study is not totally irrelevant.
• strength of bahrick et al.: high external validity

  real-life meaningful memories (e.g. of peoples faces and names) were studied. when lab studies were done with meaningless pictures to be remembered, recall rates were lower. the downside of such real-life research is that confounding variables are not controlled, such as the fact that bahrick's participants may have looked at their yearbook photos and rehearsed their memories over the years.