Memory - Coding, Capacity and Duration of Memory Flashcards
What is the definition of coding?
Coding is the format in which information is stored in the various memory stores.
What is the definition of capacity?
Capacity is the amount of information that can be held in a memory store.
What is the definition of duration?
Duration is the length of time information can be held in memory.
What is short-term memory (STM)?
Short-term memory is the limited-capacity memory store. Coding is mainly acoustic (sounds), capacity is between 5 and 9 items on average, and duration is between about 18 and 30 seconds.
What is long-term memory (LTM)?
Long-term memory is the permanent memory store. Coding is mainly semantic (meaning), it has unlimited capacity, and it can store memories for up to a lifetime.
What did Baddeley (1966a, 1966b) investigate in his research on coding?
Baddeley gave different lists of words to four groups of participants to remember:
Group 1 (acoustically similar): Words sounded similar, e.g., cat, cab, can.
Group 2 (acoustically dissimilar): Words sounded different, e.g., pit, few, cow.
Group 3 (semantically similar): Words with similar meanings, e.g., great, large, big.
Group 4 (semantically dissimilar): Words with different meanings, e.g., good, huge, hot.
Participants were shown the original words and asked to recall them in the correct order. When recalling immediately after hearing (STM recall), they did worse with acoustically similar words. When recalling after 20 minutes (LTM recall), they did worse with semantically similar words, suggesting that information is coded semantically in LTM.
What is digit span and how did Jacobs (1887) measure capacity?
Digit span measures how much information can be held at any one time. Jacobs developed a technique to measure this, where participants were given a string of digits or letters and asked to recall them in the correct order. The mean span for digits across all participants was 9.3 items; the mean span for letters was 7.3.
How did Miller (1956) contribute to our understanding of STM capacity?
Miller noted that things often come in sevens, such as days of the week and notes on the musical scale. He suggested that the capacity of STM is about 7 ± 2. People can recall 5 words as well as they can recall 5 letters by chunking—grouping sets of digits or letters into units or chunks.
What did Peterson and Peterson (1959) investigate regarding the duration of STM?
They tested 24 undergraduate students, each of whom took part in eight trials. On each trial, a student was given a consonant syllable (a trigram) to remember and a 3-digit number to count backwards from to prevent rehearsal. On each trial, they were told to stop after a retention interval of 3, 6, 9, 12, 15, or 18 seconds. After 3 seconds, average recall was about 80%. After 18 seconds, it was about 3%, suggesting that STM has a very short duration unless rehearsed.
What did Bahrick et al. (1975) find about the duration of LTM?
They studied 392 participants from Ohio aged between 17 and 74. High school yearbooks were obtained, and recall was tested via:
Photo recognition of 50 photos.
Free recall of names of their graduating class.
Participants tested within 15 years of graduation were about 90% accurate in photo recognition; after 48 years, it declined to about 70%. This shows that LTM can last a very long time indeed.
What is one evaluation point about research on coding?
One limitation of Baddeley’s study is that it used quite artificial stimuli rather than meaningful material. The word lists had no personal meaning to participants. This means we should be cautious about generalising the findings to different kinds of memory tasks. For example, when processing more meaningful information, people may use semantic coding even for STM tasks. This suggests that the findings from this study have limited application.
What is one evaluation point about research on capacity?
A limitation of Jacobs’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 as they might. This would mean 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.
What is one evaluation point about Miller’s research?
A limitation of Miller’s research is that he may have overestimated the capacity of STM. For example, Cowan (2001) reviewed other research and concluded that the capacity of STM was only about four chunks. This suggests that the lower end of Miller’s estimate (five items) is more appropriate than seven items.
What is one evaluation point about research on duration?
A limitation of Peterson and Peterson’s study is that the stimulus material was artificial. Trying to memorise consonant syllables does not reflect most real-life memory activities where what we are trying to remember is meaningful. So we might say that this study lacked external validity. However, we do sometimes try to remember fairly meaningless things, such as phone numbers, so the study is not totally irrelevant.
What is one evaluation point about Bahrick et al.’s study on LTM duration?
A strength of Bahrick et al.’s study is that it has higher external validity. Real-life meaningful memories were studied. When studies on LTM have been conducted with meaningless pictures to be remembered, recall rates were lower (e.g., Shepard 1967). The downside of such real-life research is that confounding 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.
