We forget things for two reasons, firstly the memory has disappeared- it is no longer available or secondly the memory is stored in the memory system but cannot be retrieved. The first theory is more likely to be applicable to forgetting in the short term memory and the second in the long term memory. You can differentiate between availability and accessibility. Availability is whether the information has been stored in the memory or not and accessibility is the ability or inability to retrieve information if it has been stored.
Forgetting information from the short term memory can be explained using the theories of trace decay and displacement. In reference to the multi store model of memory the theory states that in the STM both capacity and duration are limited. The capacity of STM is about 5-9 units of information and the duration of STM is given at only a few seconds, to a maximum of a minute or so. As information cannot stay indefinitely In STM, if it is not transferred into LTM it will be forgotten. Therefore theories of forgetting in STM are based on availability.
There are two main theories about how information is lost from the STM, trace decay and displacement theories. Trace decay theory of forgetting (STM) relates to both long term and short term memory and also relates to lack of availability. The theory suggests that the STM can only hold information for between 15 and 30 seconds unless it is rehearsed. After this time the information decays (fades away). This explanation of forgetting in short term memory assumes that memories leave a trace in the brain. A trace is some sort of physical/chemical change in the nervous system.
Trace decay theory states that forgetting occurs as a result of the automatic decay or fading of the memory trace. Trace decay theory focuses on time and the limited duration of short-term memory. Decay theory assumes that memories have a physical or biological basis in the brain, and that the encoding of memories involves a structural change in the brain. The physical representation of a memory is called a memory trace or an engram. This theory sees forgetting as the physical breakdown or decay of the memory trace. Assuming that rehearsal does not take place, the mere passage of time will cause the memory trace to break down.
This explains why forgetfulness increases with time. According to the theory, metabolic processes happen over time which causes the structural change to break down if it is not maintained through repetition. Strengths of the decay theory are that it appeals to common sense that if we don’t use/activate the memory we will lose it. However the theory also has weaknesses and it does not explain why some older memories (especially in those who have Alzheimer’s) are not lost and can still be remembered whereas newer memories seem to decay more easily/quicker. A theory that supports decay theory is Peterson and Peterson (1959).
They provide evidence for this theory. They conducted a study where they asked participants to recall a string of consonants selected so as to be difficult to pronounce. Recall delay was set to 3, 6, 9, 12, 15 and 18 during which rehearsal was prevented by participants counting backwards in threes from a target number (e. g. 397). Each subject was tested a total of 8 times at each of the 6 delay intervals. The findings of the study showed that while after a 3 second retention interval trigrams about 90% of trigrams were recalled, after 18 seconds only 10% were.
The duration of STM without retention is very short. In terms of decay theory, the engram could not grow stronger and so broke down. Another theory of forgetting in the short term memory is the displacement theory. This theory suggests that new information received by the STM overwrites or displaces previous information. In a system of limited capacity, forgetting would take place through displacement in STM. According to this theory, when the system is full, the new information will push the old information out.
A strength of the displacement theory would be that it provided a good account of how forgetting might take place in Atkinson and Shiffrin’s (1968) model of short term memory. However it does have its weaknesses, it did become clear that the short term memory was much more complex than Atkinson and Shiffrin proposed. Forgetting from the STM can occur due to displacement or decay but it is difficult to specify which. Forgetting information from the LTM can be explained by the decay theory; we forget things because the physical memory trace has disappeared due to the passage of time.
It can also be explained by interference theory, when one set of learning interferes with another. For example, things learned in the past may interfere with things learned now or vice versa. Or cue dependant forgetting can also explain forgetting information from the LTM. This theory suggests that information is not lost from LTM, but is simply inaccessible until an appropriate cue is given which triggers the memory. The multi store model of memory states that LTM has an unlimited capacity and memories have duration of potentially forever.
However, we know from our own lives that we o forget from LTM. But does that mean the memories are gone, or we just can’t reach them? Theories of forgetting in LTM therefore are a mixture of accessibility and availability. An experiment that supports decay theory in the long term memory is Lashley (1931) he investigated whether by making physical alterations to the brain, he could induce forgetting. If this was the case, then it would suggest that memory has a physical basis and that forgetting is a result of the decay of the memory trace. He trained rats to learn mazes and then removed sections of their brains.
He found a relationship between the amount of brain removed, and the amount of forgetting. This study supports decay theory although there are issues of ecological validity and whether it is generalizable from rats to humans. However if decay was the only explanation for loss of memory in the LTM we would expect that all memories would decay at the same time regardless of what happened in the intervening time. Generally there is little support for decay theory, as it cannot explain how we are able to remember things from many years ago.
Another theory that may be able to explain why we forget in the LTM is interference. According to this theory there are two types of interference, proactive interference and retroactive interference. Proactive interference is when previous learning interferes with later learning and retroactive interference is when later learning disrupts earlier learning. A common everyday example of proactive interference is placing household objects in a different place in a room and going back to the place where the object used to be to try and find it rather than where you have now put it.
Underwood and Postman (1960) used a pair associate learning task to test the effect of interference. Participants were asked to learn a series of word pairs, so that they can be presented with the first word (the stimulus word) and recall its paired word (response word). They are then given another list of word pairs to learn which have the same stimulus word, but a different response word. Participants have their recall tested on either the first or second list of words. As expected, recall of the response words is poorer, and affected by both previous learning (proactive) and later learning (retroactive).
However this effect is only present when the stimulus words are kept the same throughout the lists. Overall the proactive and retroactive effects are reliable and robust; however there are a number of problems with interference theory as an explanation of forgetting. Firstly, interference theory tells us little about the cognitive processes involved in forgetting. Secondly, the majority of research into the role of interference in forgetting has been carried out in a laboratory using lists of words, a situation which is likely to occur fairly infrequently in the real world.
As a result it may not be possible to generalise the findings of the studies supporting interference theory. The final theory that may explain why we forget in the LTM memory is cue dependant forgetting. This theory states that forgetting is not due to the loss of a memory, but rather is due to the inability to access it. This is known as retrieval failure. The memory is still there but it is inaccessible. The reason that it is unavailable is because you do not have the right cue. Cues can either be external (something about the environment or context) or internal (something about your own state or mood).
There is lots of evidence to support this theory of forgetting from laboratory experiments. The ecological validity of these experiments can be questioned but their findings are supported by evidence from outside the laboratory. Context dependant learning (external) was demonstrated by Abernethy (1940) who found that students who sat a test in the same room with the same teacher as their normal lessons got higher results. Therefore, the environment acted as a cue to memory in this study. Our internal mental or emotional state can also act as a cue. This is state dependant learning.
Goodwin et al (1969) found that people who had forgotten things when sober could remember once they had drunk sufficient alcohol. Repression may also cause forgetting because it causes traumatic memories to be repressed into the unconscious where they cannot be retrieved. Depression is also another factor that can cause forgetting because due to either the shrinking of the hippocampus due to a rise in cortisol of depressed people or possibly due to low motivation and inattention. Out of all the theories of forgetting discussed, you can see that not one theory covers all aspects of memory.
There are many different theories to suggest why we forget different types of information and the theory that applies depends on many things such as whether the information is stored in the STM or the LTM. Not one theory can explain every result that is given from these studies but they are matched to the theories they support the most. A theory that is supported by a particular study can also have studies going against it. For example, evidence for interference would be underwood and postman (1960 however the Tulving and Psotka (1971) study goes against the interference theory.
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Topic: Discuss Explanations of Forgetting
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