coding,capacity,duration of memory

• Study 1: Baddeley(1966)coding in stm+lmt

  Acoustically similar words(cat,cab etc) or dissimilar (pit,few etc). Semantically similar words(large,big etc) or dissimilar(good,hot etc). Immediate recall worse with acoustically similar words, STM is acoustic. Recall after 20minutes worse with semantically similar words, LTM is semantic
• limitation of baddeley - didnt use meaningful material


  The words used in the study had no personal meaning to the pp's. 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 tasks
• study 2: Jacobs (1888) capacity of STM

  Digit span: Researcher reads 4 digits and increases until the pp can't recall the order correctly. On average, pp's could repeat back 9.3 numbers and 7.3 letters in the correct order immediately after they were presented
• limitation of Jacob's study - was conducted a long time ago

  Early research in psychology often lacked adequate control of extraneous variables. For example, some pp's 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
• study 3: Miller (1956) capacity of stm


  Miller made observations of everyday practice. For example, he noted that things come in sevens : there are 7 notes on the musical scale , 7 days of the week , 7 deadly sins and so on. The span of stm is about 7 items (plus or minus)but can be improved by chunking
• limitation on miller's study research : may have 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
• study 4: Peteron + Peterson (1959) duration of stm

  24 students were given a consonant syllable (eg YCG) to remember and a 3-digit number to count backwards for 3,6,9,12,15 or 18 seconds. 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
• limitation of peterson+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. One the other hand, we do sometimes try to remember fairly meaningless things such as phone numbers. So the study is not totally irrelevant
• Study 5 : Bahrick et al (1975) duration of ltm


  Participants were 392 Americans aged between 17 and 74.

  1)Recognition test: 50 photos from pp's high school yearbook 2)Free recall test: pp's listed names of their graduating class. PP'S tested 48years after graduation were about 70% accurate in photo recognition. Free recall was less accurate
• strength of Bahrick et al's study - high external validity


  Real life meaningful memories. 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 pp's may have looked at their yearbook photos and rehearsed their memories over the years.