Why do we forget things?
Oliver Rees
According to Foster (2011) 137 for a memory system to be effective it must do three things. It must be able to encode information, store it faithfully over an indefinite period of time and it must be able to recall the stored information upon request. Memory can be divided into innumerable sub-types and this process of encoding, storage and recollection can vary in accordance with the nature of the memory being stored. These varying types of memory are often very different, however it would be wrong to assume that all memory types are stored independently. Sensory memory is a fleeting impression of the current situation in which you find yourself and only the more important aspects from this are transferred to short-term memory (STM) or working memory. STM is dealt with by the frontal cortex; according to Greenfield (2000). 138 Long-term factual (semantic) memory is often stored in the temporal cortex, whilst evidence from patients with very selective brain damage suggests the hippocampus is involved in the storage of memory of events (episodic memory) and more recent research suggests that in time these memories are transferred to the neocortex. From here we will consider the nature of normal forgetfulness in comparison to more abnormal levels of memory problems and also whether there is some biological or evolutionary reason as to why we appear to forget most of what we see, hear or do. As we will see later, memory loss caused by disease or trauma usually results in some physiological change in the brain’s anatomy, however everyone experiences some level of forgetfulness in normal life without having any apparent abnormalities in their brain. Depending on the time from the present at which the desired memory item happened the forgetfulness could indicate an issue with the 137 Foster,J.K., 2011, Memory: From sense to storage , [e-journal] 2841 Available through: New scientist database [Accessed 8 July 2012]. 138 Greenfield, S., 2000. Brain Story . London: BBC Worldwide Limited
aforementioned tripartite memory system or if it happened more recently, a misfire in the working memory or short term memory could be to blame. The explanation for the latter is perhaps more definite. It is suggested by Foster (2011) 139 that short-term memory is not stored in a physical form but more in ‘acoustic or phonological form’ and it is well acknowledged, following the work of Wundt in the 19 th century, that short-term memory can hold between 5-9 items. These items cannot remain there very long however, perhaps due to their transient state of existence. Unexceptional items being stored by this method are quickly forgotten as new impressions from the sensory organs overwrite the existing ones. However, more vivid or important memories may be committed to the so-called long-term memory system. Loss of long-term memory items is less well understood; as some studies would suggest that we do not really forget anything we see but instead find it harder to access these memories as time goes on; again indicating problems with the encoding or recall of memories. In the same article Foster also reports on these experiments, the most notable of these experiments was by Lionel Standing in 1973, in which he showed volunteers up to 10,000 photos for 5 seconds. Three days later he showed another series of photos to the volunteers and they were able to correctly identify whether it was a photo from the original sample or not with very few mistakes. Although this illustrates that some aspects of the brain’s memory capacity are perhaps limitless, in this case it would seem that the visual prompt was enough to aid the search algorithms of the brain to correctly finding the appropriate memory and it is a lot less challenging than recalling facts without 139 Foster,J.K.,2011, Memory: Forgetting and loss , [e-journal] 2841 Available through: New Scientist database [Accessed 7 July 2012].
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