STM and LTM

• coding is the format in which information is store in the various memory stores
• Peterson and Petersons' study on duration in STM:

  • procedure- 24 students were given a consonant syllable to recall and a 3 digit number to count backwards from. The retention interval was varied: 3,6,9,12,15 to 18 secs
  • findings- after 3 secs average recall was 80%. After 18 secs it was 3%. STM duration without rehearsal is 18-30 secs
• long term memory is the permanent memory store
• capacity is the amount information that can be held in a memory store
• duration is the length of time information can be held in memory
• STM is the limited-capacity memory store
• Baddeley gave 4 groups lists of acoustically/semantically similar/dissimilar words to learn then recall. When asked to immediately recall the list, the did worse on the acoustically similar words, which suggests STM coding is mainly acoustic, whereas after 20 mins they did worse on the semantically similar words which means LTM coding is semantic
• Jacob's study on capacity in STM and LTM:

  • procedure- researcher reads 4 digits and increases until the participant cannot recall the order correctly. The final number is the digit span.
  • findings- on average, participants could repeat back 9.3 numbers and 7.3 letters in the correct order
• Miller study of capacity in LTM and STM:

  • procedure- Miller observed everyday practice, noted that things come in sevens like notes of musical scale, days of the week etc.
  • findings- the span of STM is about 5-9 items but is increases by chunking/grouping sets of digits/letters into meaningful units
• Bahrick et al studied the duration of LTM:

  • procedure- participants were 392 American between ages 17-74. Recognition test was 50 photos from high school yearbooks. Free recall test was participants listing names of their graduating class
  • findings: in the recognition test, 90% accurate after 15 years, 70% after 48 years. In the free recall test, 60% recall after 25 years, 70% after 48 years
• One limitation of Peterson and Peterson's study of duration of STM is meaningless stimuli. We sometimes try to recall meaningless things so the study is not completely irrelevant. But recall of consonant syllables doesn't reflect meaningful everyday memory tasks. Therefore, the study lacked external validity.
• One strength of Baddeley's study on coding of STM and LTM is that it identified 2 memory stores. Later research showed that there are expectations to Baddeley's findings. But STM is mostly acoustic and LTM is mainly semantic. This led to the development of the multi-store model
• One limitation of Baddeley's study on coding of STM and LTM is that it used artificial stimuli. The words used had no personal meaning to the participants so tells us little about coding for everyday memory tasks. When processing more meaningful information, people use semantic coding even for STM. This means the findings of the study have limited application
• One limitation of Miller's study on capacity of STM and LTM is that it may overestimate STM capacity. For example, Cowan reviewed other research. He concluded that the capacity of STM was only 3-5 chunks. This suggests that the lower end of Miller's estimate 5 chunks is more appropriate than 7 items
• One strength of Bahrick et al. study on duration of LTMis that it had high external validity. Everyday meaningful memories like faces and names were studies. When lab studies were done with meaningless pictures to be remembered, recall rates were lower. This means that Bahrick et al. findings reflect a more 'real' estimate of the duration of LTM