Coding, capacity and duration of Memory Flashcards
What is coding?
The format in which information is stored in the various memory stores.
What is capacity?
The amount of information that can be held in a memory store.
What is duration?
The length of time information can be held in memory.
Research on coding?
Baddeley (1966):
- Group 1 (acoustically similar): words that sound similar
- Group 2 (acoustically dissimilar): words that sounded different
- Group 3 (semantically similar): words with similar meaning
- Group 4 (semantically dissimilar): words that have different meanings
Ppts were shown the original words and asked to recall them in the same order.
In STM they tended to do worse in acoustically similar words, in LTM recall they did worse with the semantically similar words, suggesting that information is encoded semantically in the LTM.
Research on capacity: digit span?
Jacobs (1887):
Ppts were asked to recall digits until failure. He found that the mean span of the digits was 9.3 and the mean span for letters was 7.3.
Research on capacity: span of memory and chunking?
Miller (1956):
He noted that things come in sevens meaning that the capacity of the STM was 7 +/- 2.
Miller also noted that people can recall 5 words as well as letters by chunking (grouping sets of digits or letters into units or chunks.)
Research on duration : STM?
Peterson and Peterson (1959):
- Tested 24 undergraduate students
- Each student took part in 8 trials
- On one trial they were given consonant syllable to remember and a 3 digit number.
- The students were asked to count backwards from the 3-digit number until told to stop to prevent mental rehearsal of the consonant syllable.
- On each trial they were told to stop after a different amount of times (3,6,9,12,15,18) seconds called retention interval.
This suggests that the STM has a very short duration unless we repeat something over and over again (verbal rehearsal.)
Research on duration: LTM?
Bahrick (1975):
- studied 392 ppts from Ohio between 17 and 74.
- they tested photo-recognition of 50 photos, some from their highschool yearbook.
- free-recall where ppts named their graduating class.
He found that ppts who were tested within 15years of graduation were 90% accurate in photo recognition. After 48 years, recall declined from 70% for photo recognition.
After 15years free recall was about 60% accurate, dropping to 30% after 48 years.
Evaluation of research into coding?
Baddeley - used artifical stimluli. Should be cautious when generalising the findings to different kinds of memory tasks.
Evaluation of Jacobs study?
Conducted a long time ago when research lacked adequate control, ppts may of been distracted, making the results not valid because confounding variables were not controlled.
(results have however been supported with other studies, supporting its validity.)
Evaluation of Millers study?
Overestimated the capacity of the STM.
Cowan (2001): reviewed other research and concluded that the capacity of the STM was about four chunks.
Evaluation of Peterson’s study?
The stimulus was artifical, so it lacks external validity.
Memory trace disappears if not rehearsed called spontaneous decay - information in the STM is displaced as it has limited capacity - ppts counted down during retention interval which could cause displacement.
Evaluation of Bahrick’s study?
High external validity, Shepard (1967) found that with meaningless pictures, recall rates are lower.
- confounding variables were not controlled however.
