mumm
-
> M
,Coding, Capacity and Duration
Research on Coding for STM and LTM
Alan Baddeley (1966a, 1966b) gave different lists of words to four groups of participants to
Key terms: remember:
• Coding: The format in which • Group 1 (acoustically similar): words sounded similar (e.g. cat, cab, can).
information is stored in the • Group 2 (acoustically dissimilar): words sounded different (e.g. pit, few, cow).
various memory stores • Group 3 (semantically similar): words with similar meanings (e.g. great, large, big).
• Capacity: The amount of • Group 4 (semantically dissimilar): words that all had different meanings (e.g. good, huge,
information that can be hot).
stored in a memory store
• Duration: The length of time Participants were shown the original words and asked to recall them in the correct order.
that information can be When they had to do this recall task immediately after hearing it (STM recall), they tended
held in a memory store to do worse with acoustically similar words.
If participants were asked to recall the word list after a time interval of 20 minutes (LTM
Short-Term Memory (STM) recall), they did worse with the semantically similar words. This suggests that information is
• STM is the limited-capacity coded semantically in LTM and coded acoustically in STM.
memory store. Coding is
mainly acoustic (sounds) and Research on Capacity (Digit Span)
capacity is bet ween 5 and 9 How much information can STM hold at any one time, i.e. what is its capacity? Joseph Jacobs
items on average, duration is (1887) developed a technique to measure digit span. The researcher gives, for example, 4
bet ween about 18 and 30 digits and then the participant is asked to recall these in the correct order out loud. If this is
seconds correct the researcher reads out 5 digits and so on until the participant cannot recall the
order correctly.
Long-term memory (LTM)
• The permanent memory This determines the individual's digit span. Jacobs found that the mean span for digits across
store. The Coding is mainly all participants was 9.3 items. The mean span for letters was 7.3.
semantic (meaning), it has
an unlimited capacity and Research on Capacity (Span of memory and Chunking)
can store memories for up to George Miller (1956) made observations of everyday practice. For example, he noted that
a lifetime things come in sevens: there are 7 notes on the musical scale, 7 days of the week, 7 deadly
sins, and so on. This suggests that the span (or capacity) of STM is about 7 items (plus or
minus 2). However, Miller also noted 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.
, Research on Duration (STM) Research on Duration (LTM)
• Margaret and Lloyd Peterson (1959) tested 24 undergraduate students. Each • Harry Bahrick and colleagues (1975) studied 392
student took part in eight trials. A 'trial' is one test. On each trial the student participants from the American state of Ohio who
was given a consonant syllable (also known as a trigram, such as YCG) to were aged bet ween 17 and 74. High school yearbooks
remember and was also given a 3-digit number. The student was then asked to were obtained from the participants or directly
count backwards from that 3-digit number until told to stop. This counting from some schools. Recall was tested in various
backwards was to prevent any mental rehearsal of the consonant syllable ways, including: (1) photo-recognition test consisting
(which would increase the student's memory for the consonant syllable). of 50 photos, some from the participant's high school
yearbook; (2) free recall test where participants
• On each trial they were told to stop after a different amount of time - 3, 6, 9, recalled all the names of their graduating class.
12, 15 or 18 seconds. This is called the retention interval. Their findings a
suggests that STM may have a very short duration indeed, unless we repeat • Participants who were tested within 15 years of
something over and over again (i.e. verbal rehearsal). graduation were about 90% accurate in photo
recognition. After 48 years, recall declined to about
Evaluation (Artificial stimuli) 70% for photo recognition. Free recall was less good
P: One limitation of Baddeley's study was that it used quite artificial stimuli than recognition. After 15 years this was about
rather than meaningful material. 60% accurate, dropping to 30% after 48 years.
E: 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.
For example, when processing more meaningful information, people may use Evaluation (high external validity)
semantic coding even for STM tasks. P: One strength of Bahrick et al.'s study is that it has
E: This suggests that the findings from this study have limited application. higher external validity because real-life meaningful
CA: However, using artificial stimuli allows for better control over variables, memories were studied.
making it easier to isolate specific aspect of memory like coding E: When studies on LTM have been conducted with
C: In conclusion it's still valid criticism that the artificial nature of the stimuli meaningless pictures to be remembered, recall rates were
reduces the study's real-world applicability. lower (e.g. Shepard 1967) showcasing the usefulness of
this study
Evaluation (lacking Validity) E: This is a strength because it provides insight into how
P: One limitation of Jacobs's study is that it was conducted a long time ago. memory works in everyday life and increases the real-
Early research in psychology often lacked adequate control. world application of this study
E: For example, some participants may have been distracted while they were CA: However, some psychologist may argue that the
being tested so they didn't perform as well as they might. downside of such real-life research is that confounding
E: This would mean that the results might not be valid because there were variables are not controlled, such as the fact that
confounding variables that were not controlled. Bahrick's participants may have looked at their yearbook
CA: However despite the age of the study, its replication by later research photos and rehearsed their memory over the years.
suggests the findings remain reliable and relevant C: In conclusion its still a strength because the use of real-
C: In conclusion its still a justified concern that the lack of control in older life memories increases the generalisability of the
studies could affect the accuracy of the original results findings
-
> M
,Coding, Capacity and Duration
Research on Coding for STM and LTM
Alan Baddeley (1966a, 1966b) gave different lists of words to four groups of participants to
Key terms: remember:
• Coding: The format in which • Group 1 (acoustically similar): words sounded similar (e.g. cat, cab, can).
information is stored in the • Group 2 (acoustically dissimilar): words sounded different (e.g. pit, few, cow).
various memory stores • Group 3 (semantically similar): words with similar meanings (e.g. great, large, big).
• Capacity: The amount of • Group 4 (semantically dissimilar): words that all had different meanings (e.g. good, huge,
information that can be hot).
stored in a memory store
• Duration: The length of time Participants were shown the original words and asked to recall them in the correct order.
that information can be When they had to do this recall task immediately after hearing it (STM recall), they tended
held in a memory store to do worse with acoustically similar words.
If participants were asked to recall the word list after a time interval of 20 minutes (LTM
Short-Term Memory (STM) recall), they did worse with the semantically similar words. This suggests that information is
• STM is the limited-capacity coded semantically in LTM and coded acoustically in STM.
memory store. Coding is
mainly acoustic (sounds) and Research on Capacity (Digit Span)
capacity is bet ween 5 and 9 How much information can STM hold at any one time, i.e. what is its capacity? Joseph Jacobs
items on average, duration is (1887) developed a technique to measure digit span. The researcher gives, for example, 4
bet ween about 18 and 30 digits and then the participant is asked to recall these in the correct order out loud. If this is
seconds correct the researcher reads out 5 digits and so on until the participant cannot recall the
order correctly.
Long-term memory (LTM)
• The permanent memory This determines the individual's digit span. Jacobs found that the mean span for digits across
store. The Coding is mainly all participants was 9.3 items. The mean span for letters was 7.3.
semantic (meaning), it has
an unlimited capacity and Research on Capacity (Span of memory and Chunking)
can store memories for up to George Miller (1956) made observations of everyday practice. For example, he noted that
a lifetime things come in sevens: there are 7 notes on the musical scale, 7 days of the week, 7 deadly
sins, and so on. This suggests that the span (or capacity) of STM is about 7 items (plus or
minus 2). However, Miller also noted 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.
, Research on Duration (STM) Research on Duration (LTM)
• Margaret and Lloyd Peterson (1959) tested 24 undergraduate students. Each • Harry Bahrick and colleagues (1975) studied 392
student took part in eight trials. A 'trial' is one test. On each trial the student participants from the American state of Ohio who
was given a consonant syllable (also known as a trigram, such as YCG) to were aged bet ween 17 and 74. High school yearbooks
remember and was also given a 3-digit number. The student was then asked to were obtained from the participants or directly
count backwards from that 3-digit number until told to stop. This counting from some schools. Recall was tested in various
backwards was to prevent any mental rehearsal of the consonant syllable ways, including: (1) photo-recognition test consisting
(which would increase the student's memory for the consonant syllable). of 50 photos, some from the participant's high school
yearbook; (2) free recall test where participants
• On each trial they were told to stop after a different amount of time - 3, 6, 9, recalled all the names of their graduating class.
12, 15 or 18 seconds. This is called the retention interval. Their findings a
suggests that STM may have a very short duration indeed, unless we repeat • Participants who were tested within 15 years of
something over and over again (i.e. verbal rehearsal). graduation were about 90% accurate in photo
recognition. After 48 years, recall declined to about
Evaluation (Artificial stimuli) 70% for photo recognition. Free recall was less good
P: One limitation of Baddeley's study was that it used quite artificial stimuli than recognition. After 15 years this was about
rather than meaningful material. 60% accurate, dropping to 30% after 48 years.
E: 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.
For example, when processing more meaningful information, people may use Evaluation (high external validity)
semantic coding even for STM tasks. P: One strength of Bahrick et al.'s study is that it has
E: This suggests that the findings from this study have limited application. higher external validity because real-life meaningful
CA: However, using artificial stimuli allows for better control over variables, memories were studied.
making it easier to isolate specific aspect of memory like coding E: When studies on LTM have been conducted with
C: In conclusion it's still valid criticism that the artificial nature of the stimuli meaningless pictures to be remembered, recall rates were
reduces the study's real-world applicability. lower (e.g. Shepard 1967) showcasing the usefulness of
this study
Evaluation (lacking Validity) E: This is a strength because it provides insight into how
P: One limitation of Jacobs's study is that it was conducted a long time ago. memory works in everyday life and increases the real-
Early research in psychology often lacked adequate control. world application of this study
E: For example, some participants may have been distracted while they were CA: However, some psychologist may argue that the
being tested so they didn't perform as well as they might. downside of such real-life research is that confounding
E: This would mean that the results might not be valid because there were variables are not controlled, such as the fact that
confounding variables that were not controlled. Bahrick's participants may have looked at their yearbook
CA: However despite the age of the study, its replication by later research photos and rehearsed their memory over the years.
suggests the findings remain reliable and relevant C: In conclusion its still a strength because the use of real-
C: In conclusion its still a justified concern that the lack of control in older life memories increases the generalisability of the
studies could affect the accuracy of the original results findings
