coding, capacity and duration of memory

Question 1

research on coding

Answer 1

alan baddeley (1966a, 1966) gave different lists of words to 4 groups of participants to remember:
group 1 - acoustically similar words : words sound similar (e.g. cat, cab, can)
group 2 - acoustically dissimilar words : words sound different (e.g. pit, few, cow)
group 3 - semantically similar words : words with similar meanings (e.g. great, large, big)
group 4 - semantically dissimilar words : words with different meanings (e.g. good, huge, hot)

participants were shown the original words and asked to recall them in the correct order.

Question 2

findings on coding

Answer 2

when they did this task immediately, recalling from short-term memory, they tended to do worse with acoustically similar words.

when they recalled the word list after a time interval of 20 minutes , recalling from long-term memory, they did worse with semantically similar words.

these findings suggest that information is coded acoustically in STM and semantically in LTM

Question 3

research on capacity

Answer 3

joseph jacobs (1887) found out capacity by measuring digit span.
for example, the researcher reads out four digits and the participant recalls these out loud in the correct order. if this is correct the researcher reads out 5 digits and so on until the participant cannot recall the order correctly. this indicated the individuals digit span.

jacobs found that the mean span for digits across all participants was 9.3 items. the mean span for letters was 7.3.

Question 4

george miller (1956)

Answer 4

made observations of everyday practise. for example, he noted that things come in seven notes on the musical scale, seven days of the week, seven deadly sins etc.
miller thought that the span (i.e. capacity) of STM is about 7 items, plus or minus 2. but he also noted that people can recall five words as easily as they can recall 5 words as easily as they can recall 5 letters.
we do this by chunking.

Question 5

chunking

Answer 5

grouping sets of digits or letters into units or chunks.

Question 6

research on duration of STM

Answer 6

margaret and peterson (1959) tested 24 students in 8 trials. on each trial the student was given a consonant syllable (YGU) to remember and also a 3 digit number (478). the student counted backwards from this number until told stop.
the counting backwards was to prevent mental rehearsal of the consonant syllable.
on each trial they were told to stop after varying periods of time: 3, 6, 9, 12, 15, or 18 seconds (the retention interval)

Question 7

findings on duration of STM

Answer 7

• after 3 seconds, average recall was 80%
• after 18 seconds, it was about 3%

peterson and petersons findings suggested that STM duration may be about 18 seconds, unless we repeated information over and over (i.e. verbal rehearsal)

Question 8

research on duration of LTM

Answer 8

harry bahrick et al (1957) studied 392 american participants aged between 17 and 74.
high school yearbooks were obtained from the participants or directly from some schools. recall was tested in some various ways, including:
1. photo-recognition test consisting of 50 photos,
some from the participants high school yearbooks
2. free recall test where participants recalled all the names of their graduating class.

Question 9

findings on duration of LTM

Answer 9

• participants tested within 15 years of graduation were about 90% accurate in photo recognition.
• after 48 years, recall declined to about 70% for photo recognition.

free recall was less accurate than recognition:
- about 60% after 15 years , dropping to 30 % after 48 years.

this shows that LTM may last up to a lifetime for some material.

Question 9

capacity

Answer 9

the amount of information that can be held in a memory store.

Question 9

coding

Answer 9

the format in which information is stored in the various memory stores.

Question 10

duration

Answer 10

the length of time information can be held in memory.

Question 11

STM

Answer 11

the limited-capacity memory store. in STM, coding is mainly acoustic (sounds), capacity is between 7 +/- 2 items, duration is about 18 seconds.

Question 12

LTM

Answer 12

the permanent memory store. in LTM, coding is mainly semantic (meaning), it has unlimited capacity and can store memories up to a life time.

Question 13

strength - research on coding

Answer 13

p - one strength of baddeley’s study is that it identified a clear difference between two memory stores.

e - STM + LTM

e - later research showed that STM uses mostly acoustic coding and LTM mostly semantic coding.

l - therefore this shows an important understanding of the memory system which led to the multi-store model.

Question 14

limitation - research on coding

Answer 14

p - one limitation of baddeley’s study was that it used quite artificial stimuli rather than meaningful material.

e - the word list had no personal meaning to participants.

e - baddeley’s findings may not tell us much about coding in different kinds of memory tasks, especially in everyday life. when processing more meaningful information, people may use semantic coding even for STM tasks.

l - this suggests that the findings from this study may have limited application.

Question 15

strength - research on capacity

Answer 15

p - one strength of jacobs’ study is its validity

e - it has been replicated, however research in psychology often lacked adequate controls.

e - some participants digit spans might have been underestimated because they were distracted during testing (confounding variables).

l - despite this, jacobs findings have been confirmed by other, better controlled studies (e.g. bopp and verhaeghen 2005). this suggests that jacobs’ study is a valid test of digit span in STM

Question 16

limitation - research on capacity

Answer 16

p - one limitation of millers research is that he overestimated STM capacity.

e - nelson cowan (2001) reviewed other research and concluded that the capacity of STM is only about 4 chunks.

l this suggests that the lower end of millers estimate (5 items) is more appropriate than 7 items.

Question 17

limitation - research on duration

Answer 17

p - one limitation of peterson and peterson’s study is that the stimulus material was artificial.

e - consonant syllable and 3-digit number.

e - the study is not completely irrelevant because we do sometimes try to remember fairly meaningless material (e.g. phone numbers). even so, recalling consonant syllables does not reflect most everyday memory activities where what we are trying to remember is meaningful.

l - this means the study lacked external validity.

Question 18

strength - research on duration

Answer 18

p - one strength of bahrick et al. study is that it has high external validity.

e - when studies on LTM were conducted with meaningless pictures to be remembered, recall rates were lower (e.g. shepard 1967)

e - therefore this is a strength because researchers investigated meaningful memories (i.e. of peoples names and faces).

l - this suggests that bahrick et al. findings reflect a more ‘real’ estimate of the duration of LTM.