Coding,capacity and duration of memory Flashcards
What is the research on coding?
- Coding is the process of converting information between 2 different forms
- Alan Baddeley gave different lists of words to 4 groups of participants to remember:
-GROUP 1 ( ACOUSTICALLY SIMILAR) (SOUNDED SIMILAR) CAT, CAB, CAN
-GROUP 2 ( ACOUSTICALLY DISSIMILAR) (SOUNDED DIFFERENT) PIT, FEW, COW
-GROUP 3 (SEMANTICALLY SIMILAR) (SIMILAR MEANING) GREAT, LARGE, BIG
-GROUP 4 (SEMANTICALLY DISSIMILAR) (DIFFERENT MEANING) GOOD, HUGE, HOT - Participants were shown the original words and asked to recall them in the correct order. 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 20mins recalling from long term memory they did worse with the semantically similar words.
- These findings suggest that information is coded aucoustically in STM and semantically in LTM
Research On Capacity
DIGIT SPAN
- How much information can the STM hold at one time? What is capacity?
- Joseph Jacobs found out by measuring the digit span
E.g. The researcher reads out 4 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 participants cannot recall the order correctly. This indicates the individual’s digit span.
- Jacobs found that the mean span for digits across all participants was 9.3. The mean span for letters was 7.3
SPAN OF MEMORY AND CHUNKING
- George Miller made observation of everyday practice.
- E.g. He noted that things come in sevens: seven notes on the musical scale and seven days of the week
- Miller thought that the span (capacity) of STM is about 7 items, plus or minus 2. But he also noted that people can recall 5 words as easily as they can recall 5 letters. We do this by CHUNKING- grouping sets of digits or letters into units or chunks.
Research on duration of STM
Margret and Peterson tested 24 students in 8 trials each. On each trail the student was given a constant syllable to remember. They were also given 3 digit number. The student had to count backwards from this number until told to stop. The counting backwards was to prevent any mental rehearsal of the consonant syllable, which would increase the duration of he STM memory. On each trial they were told to stop after varying periods of time: 3,6,9,12,15 or 18 seconds (retrieval interval). After 3 seconds average recall was about 80% after 18 seconds it was about 3%.
-Peterson and Peterson’s findings suggested that STM duration may be about 18 seconds, unless we repeat the information over and over (verbal rehearsal)
Research duration of LTM
Barick et al studied 329 American participants aged between 17 and 74. High school yearbooks were obtained from participants or directly from some schools. Recall was tested in various ways including- photo recognition test consisting of 50 photos, some from the participants high school yearbooks, free recall test where participants recalled all the names of their graduating class.
- 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.
Why is separate memory stores a strength of Baddeley’s?
One strength of Baddeley’s study is that it identified a clear difference between two memory stores.
- Later research showed that there are some expectations to Baddely’s findings. But the idea that STM uses mostly acoustic coding and LTM mostly semantic has stood the test of time. This was an important step in our understanding of the memory system, which led to the multi-store model.
Why is artificial stimuli a disadvantage of Baddeley’s study?
One limitation of Baddeleys study was that it used quite artificial stimuli rather than meaningful material.
For example the word lists had no personal meaning to participants. So Baddelys findings may no 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.
- This suggests that the findings from this study have limited application.
Why is valid study a strength of Jacobs’ study?
One strength of Jacobs study is that is has been replicated.
The study is a very old one and early research in psychology often lacked adequate controls.
For example some participants digit spans might have been underestimated because they were distracted during testing (confounding variables). Despite this Jacobs’ findings have been confirmed by other, better controlled studies.
This suggests that Jacobs’ study is a valid test of digit span in STM.
Why is not so many chunks a limitation of Miller’s research?
One limitation of Miller’s research is that he may have overestimated STM capacity.
Cowan reviewed other research and concluded that the capacity of STM is only about 4+ - 1 chunks.
This suggests that the lower end of Miller’s estimate 5 items is more appropriate than seven items
Why is meaningless stimuli in STM study a limitation?
One limitation of Peterson and Peterson’s study is that the stimulus material was artificial.
The study is not completely irrelevant because we do sometimes try to remember fairly meaningless material eg. phone number. Even so recalling consonant syllables does not reflect most everyday memory activities where we are trying to remember is meaningful.
This means the study lacked external validity.
Why is high external validity a strength in Barick et al’s study?
One strength of Barick et al’s stdy is that it has high external validity. This is because the researchers investigated meaningful memories ie. peoples names and faces. When studies on LTM were conducted with meaningless pictures to be remembered, recall rates were lower.
This suggests that Barick et al’s findings reflect a more real estimate of the duration of LTM.
