Coding, Capacity and Duration of Memory Flashcards
Coding:
The format in which information is stored in the various memory stores.
Capacity:
The amount of information that can be held in memory store.
Duration:
The length of information can be held in memory.
STM:
The limited-capacity memory store. Coding is mainly acoustic (sounds), capacity is between 5 and 9 items on average duration is between
about 18 and 30 seconds.
LTM:
The permanent memory store. Coding is mainly semantic meaning it has unlimited capacity and can store memories for a lifetime.
Coding: *
Once information gets into the memory system, it is stored in different formats depending on the memory store. The process of converting information from one form to another is called coding.
Research on Coding:
Alan Baddeley (1966a, 1966b) gave different lists of words to 4 groups of pps to remember:
1. Group 1: acoustically similar (sound the same).
2. Group 2: acoustically dissimilar (sound different).
3. Group 3: semantically similar (words with similar meanings).
4. Group 4: semantically dissimilar (words with different meanings).
Research on Coding Results:
- Participants were shown the words and asked to recall them in the right order.
- When they were asked to recall them in the right order immediately, STM, they tended to worse with acoustically similar words.
- If they were asked to recall the words list after 20 minutes (LTM) they did worse with the semantically similar words.
- Information is coded semantically in LTM.
Research on Capacity: Digital Span
- Joseph Jacobs (1887) developed a technique to measure a digit span.
- The researcher gives,for example 4 digits, and then they are asked to recall it in the correct order out loud.
- They continue with more numbers until they cannot recall the order correctly, digit span.
- The mean span for digits was 9.3 items, mean for letter was 7.3
Research on Capacity: Span of memory and chunking
- George Miller (1956) made observation of everyday practice.
- He noted that things come in sevens: 7 notes on the musical scale, 7 days, 7 deadly sins.
- The span of STM is about 7 items plus or minus 2.
- Miller also noted that people can recall 5 words as well as they can recall 5 letters, by chunking.
Research on Duration: STM
- Margaret and Lloyd Peterson (1959) tested 24 undergraduate 24 students.
- Each student took part in 8 trials and on each trial the student was given a consonant syllable to remember and 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 was to prevent any mental rehearsal of the consonant syllable.
- On each trial they were told to stop after a different amount of time (3,6,9,12,15,18). This is called the retention interval.
- It suggests that STM may have a very short duration.
Research on Duration: LTM
- Harry Bahrick and colleagues (1975) and studied 392 participants from Ohio aged between 17-74.
- High school yearbooks were obtained from the pps or directly from some schools. Recall was tested: photo-recognition test consisting of 50 photos and free recall test where participants recalled all the names of their graduating class.
- Participants tested within 15 years were 90% pr and 60% fr. 48 years recall for pr was 70% then 30% fr.
- This shows that LTM can last a very long time indeed.
E: Artificial Stimuli
- Baddeley’s study used quite artificial stimuli rather than meaningful material.
- The word lists had no personal meaning to participants.
- Have to be cautious about generalising the findings to different kinds of memory task.
- When processing more meaningful information, people may use semantic coding even for STM tasks.
- Limited application.
E: Lacking Validity
- One limitation of Jacob’s study is that it was conducted a long time ago.
- Early research in psychology often lacked adequate control.
- For example, some participants may have been distracted while they were being tested so they didn’t perform as well they might.
- This would mean that the results might not be valid because there were confounding variables that were not controlled.
- However, the results of this study have been confirmed in other research, supporting its validity.
E: Not so many chunks
- One limitation of Miller’s research is that he may have overestimated the capacity of STM.
- Cowan (2001) reviewed other research and concluded that the capacity of STM was only about 4 chunks.
- This suggests that the lower end of Miller’s estimate (5 items) is more appropriate than 7 times.
E: Meaningless Stimuli in STM study
- P2 study is that the stimulus material was artificial.
- Trying to memorise consonant syllables does not reflect most real-life memory activities where what were are trying to remember is meaningful.
- Lacked external validity.
- However, we do sometimes try to remember fairly meaningless things like phone numbers.
E: Higher External Validity
- One strength of Bahrick et al’s study is that has higher external external validity as real life meaningful memories were studied.
- Studies on LTM have been conducted with meaningless pictures recall rates were lower (Shepard 1967).
- The downside of such real-life research is that confounding variables were not controlled.
- Bahrick’s participants may have looked at their yearbook photos and rehearsed their memory over the years.
E: Criticising Peterson and Peterson
- One explanation for why we forget things in STM is that the memory trace simply disappears if not rehearsed (spontaneous decay).
- An alternative explanation is that information in STM is dispalced.
- STM has a limited capacity and any new information will push out what is currently here.
- In the study by Peterson and Peterson participants counted down during the retention interval.
