The theories of memory and how much, or how long we can remember things, and why, is a greatly studied area of Psychology as a science. Psychologists have created and recreated numerous tests and research methods in order to prove that their particular theory is correct. There are two main theories of memory: Levels of Processing (L.O.P.) and the Multi-store Model. The L.O.P. approach was pioneered by two psychologist Craik and Lockhart (1972), who believed that the mind will remember things better if the information is processed on a deeper level, ie. thought about more, taking into account the amount of ‘work’ that is put into processing the information received. From research they discovered that the deeper the processing required the longer and more durable the memory is likely to be. They also identified what they believed to be three levels of processing:
Structural – What something looks like. Phonetic – What something sounds like. Semantic – What something means. From experiments and tests carried out, they found that the deepest level was semantic, and their reason for this, they argued, was because in order to extract the meaning from a word, and to consider it’s relevance in a sentence of words, requires a lot of processing. They decided that hearing a word and then trying to visualize it also requires some extensive cognitive processing, but not as much as semantic processing, and the least amount of mental work was required for structural processing, ie. what the letters look like. A test carried out by Craik and Tulving (1975), ‘Depth of processing and retention of words in episodic memory’ supported their theory.
Another model which is highly regarded as one of the most influential theories of memory is the Multi-store model, in particular the two-process model, designed and tested by Atkinson and Shiffrin (1968, 1971). Their theory was that information received by the senses is primarily stored in the sensory store for a very short period of time before it is transferred to the short term memory. Atkinson and Shiffrin believed that when the information is in the short term memory (STM), it could either be rehearsed for a certain amount of time and then stored in the long term memory (LTM), or alternatively lost. Figure 1.1 illustrates the theory in an easier to understand way. Perhaps this is also an example of how the L.O.P. theory is flawed as although the diagram is seen to be structural information, it will probably provoke strong visual imagery.
Atkinson and Shiffrin believed that ‘chunks’ of information received by the sensory store could be held in the STM for around 20 seconds, but only 5 to 9 (on average) chunks of info can be remembered without rehearsal. However, if rehearsed the chunks of information can be transferred into the long term memory and more items can be remembered. The theory of the rehearsal loop interests me, so I decided to look further into it and found that psychologists: Brown (1958) and Peterson and Peterson (1959) independently discovered a method for testing the existence of the rehearsal loop called the Brown-Peterson technique.
This basically involves a list of trigrams (three letter words made up of consonants with no immediate meaning ie. BKD, as apposed to WHY) shown to subjects for 20 seconds, rehearsed for 25 seconds and then recorded in order by the subject as well as possible. The same list is then shown to another subject for the same amount of time, however this time the 25 seconds rehearsal time will be interrupted with an interference task ie. counting backwards in threes from the number 58. This is the technique I will use as a basis of my mini-cognitive research project.
AIM: To test the existence of the rehearsal loop by preventing it from its task with an interference task during the rehearsal time. RATIONALE: I will be re-creating the Brown-Peterson technique for testing the existence of the rehearsal loop, although my study will use slightly different trigrams, and obviously a different set of people. I’m interested to check whether the results of my study will support the results found by Brown-Peterson or not. I will use a set word list for both groups of people studied and I’m expecting the results of my study to support the results of previous tests, thus supporting the theory of existence of the rehearsal loop.
HYPOTHESIS: When asked to recall the list of trigrams in order after a period of 25 seconds rehearsal time, the subject will remember significantly more trigrams if the rehearsal time is not interrupted by an interference task. NULL HYPOTHESIS: Subjects taking part in the experiment will not recall a significantly greater number of words whether their rehearsal time is interrupted with an interference task or not. Any difference found is purely down to chance.
METHOD: The method I chose to use in order to obtain the clearest and most reliable data was the laboratory experiment. The reason for using this method is to reduce the amount of extraneous and possibly confounding variables which could interfere with the results; also it becomes very easy to repeat the same test over and over without change. I will use the independent groups design to ensure that different participants are used for each test in order to avoid the chances that the participants will skew the results through rehearsal.
The first set of participants will be shown a list of 15 trigrams for 20 seconds, after which time they will be asked to rehearse these for a period of 25 seconds. After that time they will then be asked to write out as many as possible in the correct order (if the trigram is BHD then the participant must write BHD, no mark will be given for BDH). The results will then be recorded. The same set of trigrams will then be shown to a different set of participants for the same amount of time. This time however during the 25 seconds rehearsal time, the participants will be asked to perform an interference task, which will be counting backwards in sets of 4 from the number 295. After the 25 seconds, they too will be asked to recall the trigram list and their results will also be recorded.