There are two main types of memory, short term and long term memory; short term memory has a limited capacity and duration. Capacity is, the amount of information someone can store in their memory. The capacity of short term memory is between 5-9 things. Coding is the format of which things are stored in our memory. Duration is the amount of time we can remember something for. Short term memory has duration of between 18-30 seconds. There have been various amounts of research done by different people on capacity, duration and coding.
Firstly research on capsid was done by joseph Jacobs. Jacobs developed the theory that how much someone could remember could be tested by using digit span. During this test a research would read 4 digits and a participant would have to read the 4 digits back, if the participants read them back correctly the researcher would then 5 digits and the participant would do the same before. This process was repeated increasing the number of letters by one each time until the participant got one of them wrong. This process was done with numbers and letters, doing this determines the duration of someone’s digit span. With this research Jacobs found that the mean across all participants was number of times was 9.3, the mean across letters was 7.3. This research was very useful but it did have its downfall. Jacobs research was lacking in validity, there could have been a lot of confounding variables that wouldn’t have been controlled things like, the participants being distracted, not giving full concentration and other things on their mind etc. this would mean that Jacobs results would have been less accurate.
Another piece of teacher done on capacity was done by a man called George Miller. Miller based his research from examples of everyday life. Miller suggested that things came in groups of sevens. Seven days in a week, seven notes on a musical scale etc. this lead to miller believing that we were accustomed to the number seven, this meant that miller believed we remembered things in sevens with an acceptation of two less or two more, meaning that we could remember things from a range of 5-9 things at a time. Miller also suggested people used a method called chunking to remember things, he said that letters and numbers can be remembered in 5’s just as well as words can be remembered in fives. Grouping things together is chunking the information which is why it’s called chunking. One problem that has been found with miller’s research is that, he made an over estimation on how much someone can chunk information, later research done by Cowan in 2001 suggested things can be chunked in groups of 4.
Coding is the way information is stored. Allan Baddeley researched into coding; he took four groups of people and gave each a list of words to remember. Group one was given acoustically similar words; words that sounded similar (e.g. cat cap can). Group two were given acoustically dissimilar words; words that sound different (e.g. cow pit few). Group three were given words that are semantiallcally similar; words that have a similar meaning (e.g. large, big, and huge). Finally group four were given words that were semantically dissimilar; words that have different meanings (e.g. food, huge, hot). The participants were asked to repeat the words back in the same order; this is called short term memory recall. Baddeley found that the participants got the most wrong of the acoustically similar words. When the participants were asked to repeat the words back after twenty minutes they got more wrong of that semantically similar words. This suggested that information in the long term memory was coded semantically. Baddeley’s research was great for learning a lot about coding but it used artificial stimuli meaning the material was meaningless. The information he was asking people to remember had no meaning, this meant that it would have been harder to remember. He had to be cautious of generalisation, if someone was remembering something personal to them they use sematic coding, concluding that findings in this study only have a limited use.
Finally research was done on duration. Duration is how long you can remember something, in the case of short term memory this is between 18-30 seconds. Margret and Lloyd Peterson. They did a test on 24 students; they did eight trials on each student. In each of the eight testes the student were given letters in a trigram e.g. YCG. The students had to count backward until someone told them to stop. Doing this would prevent any rehearsal of the trigram letters, if they rehearsed the trigram letters they would be transferred into their long term memory and it would defeat the point of the study. During each of the trials they were told to stop counting back after 3, 6, 9, 12, 15, and 18 seconds. This is called a retention interval; the amount of time that occurs between a learning stage and memory recall stage. After each of the time periods the students would say the trigram letter so see if they had remembered. In the reaserch Peterson and Peterson deduced that the smaller the retention interval they more likely they were to remember it. This proved that short term memory had a short duration unless there had been some sort of revising happening of what was being tried to remember e.g. verbal rehearsal. The research that Peterson and Peterson did was valuable, but the stimulus had artificial material. Remembering letters isn’t a good example of different things we try to remember in real life situations. Even though we remember things like phone numbers the study didn’t have much other use to everyday life. This means the study didn’t have external validity.