Coding, capacity and duration of memory
Research on coding- the process of converting information from one form to another
is called coding. Alan Baddeley (1966) gave different lists of words to four groups
of participants to remember: group 1 (acoustically similar), group 2 (acoustically
dissimilar), group 3 (semantically similar), group 4 (semantically dissimilar).
Participants were shown the original words and asked to recall them in the correct
order. When they had to do this recall task immediately after hearing it (STM
recall), they tended to do worse with acoustically similar words. If participants
were asked to recall the word list after a time interval of 20 minutes (LTM
recall), they did worse with the semantically similar words. This suggests that
information is coded semantically in LTM
Limitation: artificial stimuli- (point) one limitation of Baddeley’s study was that
it used quite artificial stimuli rather than meaningful material. (explain) the
word lists had no personal meaning to participants. This means we should be
cautious about generalising the findings to different kinds of memory task
(evidence) when processing more meaningful information, people may use semantic
coding even for STM tasks. (link) this suggests that the findings from this study
have limited application.
Research on capacity- digit span: Joseph Jacobs (1887) developed a technique to
measure digit span. The researcher gives 4 digits then the participant is asked to
recall these in the correct order out loud. If this is correct, the researcher
reads out 5 digits and so on until the participant cannot recall the order
correctly. This determines 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. span of memory and chunking: George Miller (1956) made observations of
everyday practice. For example, he noted that things come in sevens. This suggests
that the span of STM is about 7 items (plus or minus 2). However, Miller also notes
that people can recall 5 words as well as they can recall 5 letters. They do this
by chunking- grouping sets of digits or letters into units or chunks
Limitation: lacking validity- (point) one limitation of Jacob’s study is that it
was conducted a long time ago. Early research in psychology often lacked adequate
control. (evidence) some participants may have been distracted while they were
being tested so they didn’t perform as well as they might. (explain) this would
mean that the results might not be valid because there were cofounding variables
that were not controlled. (link) although this means there is lacking validity, the
results of the study have been confirmed in other research, supporting its
validity.
Limitation: not so many chunks- (point) one limitation of Miller’s research is that
he may have overestimated the capacity of STM (evidence) Cowan (2001) reviewed
other research and concluded that the capacity of STM was only about four chunks.
(link) this suggests that the lower end of Miller’s estimate (five items) is more
appropriate than seven items.
, Research of STM – duration of STM: Margaret and Lloyd Peterson (1959) tested 24
undergraduate students. Each student took part in eight trials. On each trial the
student was given a consonant syllable to remember and was also given a 3-digit
number. The student was then asked to count backwards from that 3-digit number
until told to stop. This counting backwards prevented any mental rehearsal of the
consonant syllable. On each trial they were told to stop after a different amount
of time - 3,6,9,12, 15 or 18 seconds. This is called the retention interval. It
suggests that STM may have a very short duration indeed, unless we repeat something
repeatedly (verbal rehearsal)
Duration of LTM: Harry Bahrick and colleagues (1975) studied 392 participants from
the American state of Ohio who were ages between 17 and 74. High school yearbooks
were obtained from the participants or directly from some schools. Recall was
tested in various ways, including 1) photo recognition test consisting of 50
photos, some from the participants high school yearbook; 2) free recall test where
participants recalled all the names of their graduating class. Participants who
were tested withing 15 years if graduation were about 90% accurate in photo
recognition. After 48 years, recall declines to about 70% for photo recognition.
Free recall was less good than recognition. After 15 years this was about 60 %
accurate, dropping to 30% after 48 years. This shows that LTM can last a very long
time.
Limitation: meaningless stimuli in STM study- (point) a limitation of Peterson and
Peterson’s study is that the stimulus material was artificial. (explain) Trying to
memorise consonant syllables does not reflect most real-life memory activities
where what we are trying to remember is meaningful. (link) This means that the
study lacked external validity. However, we do sometimes try to remember
meaningless things, such as phone numbers, so the study is not totally irrelevant.
Strength: higher external validity- (point) one strength of Bahrick et al.’s study
is that it has higher external validity. (evidence) Real-life meaningful memories
were studied. When studies on LTM have been conducted with meaningless pictures to
be remembered, recall rates were lower (Shepard 1967). (evidence) the downside of
such real-life research is that cofounding variables are not controlled, such as
the fact that Bahrick’s participants may have looked at their yearbook photos and
rehearsed their memory over the years.
Research on coding- the process of converting information from one form to another
is called coding. Alan Baddeley (1966) gave different lists of words to four groups
of participants to remember: group 1 (acoustically similar), group 2 (acoustically
dissimilar), group 3 (semantically similar), group 4 (semantically dissimilar).
Participants were shown the original words and asked to recall them in the correct
order. When they had to do this recall task immediately after hearing it (STM
recall), they tended to do worse with acoustically similar words. If participants
were asked to recall the word list after a time interval of 20 minutes (LTM
recall), they did worse with the semantically similar words. This suggests that
information is coded semantically in LTM
Limitation: artificial stimuli- (point) one limitation of Baddeley’s study was that
it used quite artificial stimuli rather than meaningful material. (explain) the
word lists had no personal meaning to participants. This means we should be
cautious about generalising the findings to different kinds of memory task
(evidence) when processing more meaningful information, people may use semantic
coding even for STM tasks. (link) this suggests that the findings from this study
have limited application.
Research on capacity- digit span: Joseph Jacobs (1887) developed a technique to
measure digit span. The researcher gives 4 digits then the participant is asked to
recall these in the correct order out loud. If this is correct, the researcher
reads out 5 digits and so on until the participant cannot recall the order
correctly. This determines 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. span of memory and chunking: George Miller (1956) made observations of
everyday practice. For example, he noted that things come in sevens. This suggests
that the span of STM is about 7 items (plus or minus 2). However, Miller also notes
that people can recall 5 words as well as they can recall 5 letters. They do this
by chunking- grouping sets of digits or letters into units or chunks
Limitation: lacking validity- (point) one limitation of Jacob’s study is that it
was conducted a long time ago. Early research in psychology often lacked adequate
control. (evidence) some participants may have been distracted while they were
being tested so they didn’t perform as well as they might. (explain) this would
mean that the results might not be valid because there were cofounding variables
that were not controlled. (link) although this means there is lacking validity, the
results of the study have been confirmed in other research, supporting its
validity.
Limitation: not so many chunks- (point) one limitation of Miller’s research is that
he may have overestimated the capacity of STM (evidence) Cowan (2001) reviewed
other research and concluded that the capacity of STM was only about four chunks.
(link) this suggests that the lower end of Miller’s estimate (five items) is more
appropriate than seven items.
, Research of STM – duration of STM: Margaret and Lloyd Peterson (1959) tested 24
undergraduate students. Each student took part in eight trials. On each trial the
student was given a consonant syllable to remember and was also given a 3-digit
number. The student was then asked to count backwards from that 3-digit number
until told to stop. This counting backwards prevented any mental rehearsal of the
consonant syllable. On each trial they were told to stop after a different amount
of time - 3,6,9,12, 15 or 18 seconds. This is called the retention interval. It
suggests that STM may have a very short duration indeed, unless we repeat something
repeatedly (verbal rehearsal)
Duration of LTM: Harry Bahrick and colleagues (1975) studied 392 participants from
the American state of Ohio who were ages between 17 and 74. High school yearbooks
were obtained from the participants or directly from some schools. Recall was
tested in various ways, including 1) photo recognition test consisting of 50
photos, some from the participants high school yearbook; 2) free recall test where
participants recalled all the names of their graduating class. Participants who
were tested withing 15 years if graduation were about 90% accurate in photo
recognition. After 48 years, recall declines to about 70% for photo recognition.
Free recall was less good than recognition. After 15 years this was about 60 %
accurate, dropping to 30% after 48 years. This shows that LTM can last a very long
time.
Limitation: meaningless stimuli in STM study- (point) a limitation of Peterson and
Peterson’s study is that the stimulus material was artificial. (explain) Trying to
memorise consonant syllables does not reflect most real-life memory activities
where what we are trying to remember is meaningful. (link) This means that the
study lacked external validity. However, we do sometimes try to remember
meaningless things, such as phone numbers, so the study is not totally irrelevant.
Strength: higher external validity- (point) one strength of Bahrick et al.’s study
is that it has higher external validity. (evidence) Real-life meaningful memories
were studied. When studies on LTM have been conducted with meaningless pictures to
be remembered, recall rates were lower (Shepard 1967). (evidence) the downside of
such real-life research is that cofounding variables are not controlled, such as
the fact that Bahrick’s participants may have looked at their yearbook photos and
rehearsed their memory over the years.
