The Human Memory
“Human memory is a marvellous but fallacious instrument. The memories which lie within us are not carved in stone; not only do they tend to become erased as the years go by, but often they change, or even increase by incorporating extraneous features”- Italian writer and chemist Primo Michele Levi.
Indeed, human memory has always fascinated writers, philosophers and researchers as it is very complex in its structure and functionality. Although, much research work has been carried out to provide an accurate explanation of the structure and functions of human memory, yet there is not a singular theory that has been till date accepted unanimously by all the researchers. However, there are two models i.e the the Dual-Store model by Atkinson and Shiffrin (1968) and the Working memory model by Baddeley and Hitch (1986-74) that have contributed significantly to have a fair understanding of the structure as well as functions of the human memory. Forgetting is also a fascinating aspect related to human memory and many theories has been proposed till date to understand the causes of forgetting.
According to the Dual-Store model of Atkinson and Shiffrin (1968), memory has three distinct memory stores i.e. sensory memory, short-term memory and the long-term memory. Of these, the sensory memory store was added later on. Hence, the model is also known as Multi-Store model. According to this model, information is detected or perceived by our sense organs and then goes into the sensory memory. “The first component in the Atkinson-Shiffrin information processing memory model is sensory memory or storage, also known as immediate memory or the sensory register” (Dehn, chapter.2). The information then goes into the short-term memory. Continuous rehearsal of the information stored in the short-term memory (STM) makes its way to the long-term memory (LTM) or else is forgotten i.e. lost from the STM by displacement or decay. “The LTM is seen as a more passive store of information which is available for retrieval but not kept in an activated form” (Groome et al , p.182). This model is in compliance with the contemporary neuro-psychological data findings and be look forwarded as in future, more researchers can arrive with their own research findings to add more into this model.
The working memory model suggested by Baddeley and Hitch (1974-2000) states that the human memory structure and function is not that too simple as proposed by Atkinson and Shiffrin. Baddeley modifies this memory model in 1986 for presenting a more accurate model of the short-term memory. In the working model, the STM has been replaced by the working memory which has a central executive for an able control and co-ordination of the two sub-system operations i.e. phonological loop and the visuo-spatial scratch pad. “The phonological loop is analogous to an audio tape recorder lop of specific length....The phonological loop has a specific function and is limited in the type of information it stores” (Dehn, chapter.2). The phonological loop again has two sub-systems - Phonological store and Articulatory control process. Visuo-spatial scratch pad on the other hand is visuo spatial working memory that holds and manipulated any information in the domain of visuo spatial. In the year 2000, Baddeley added another component to explain the structure and function of human memory in this model and named it ‘episodic buffer’. “One of the advantages of the episodic buffer concept is that it provides a bridge between the Baddeley and Hitch working memory model” (Baddeley, chapter-8). The episodic buffer mainly acts as a backup store.
The Dual Store model of human memory has been criticized by many because of its utmost simplicity in explaining the otherwise complex structure and function of the human theory. It stress about the need of rehearsal so that information can make its way from the STM to the LTM or otherwise it get lost. However, this has been questioned by other researchers. “Hyde and Jenkins (1973) study aimed to see if there is a difference between intentional and incidental learning of word lists. Their findings showed that there was no difference in the number of words recalled” (Redshaw 2009, p. 51). Further, it is a well known fact that many students revise their lessons thoroughly before exams, but fail to recall them during examination while at the same time, remember any information once glanced in a celebrity magazine for a longer duration. The Dual Store model suggests that STM and LTM works in a uniform fashion and are two distinct units, but a case study by Shallice and Warrington (1970) establishes the fact that STM has distinct parts to process various types of information and rehearsal is not the only option of information transfer from STM to LTM. They conducted a series of psychological tests on many patients and found one patient named KF who was not able to remember numbers as done by others but his long term memory was found to be intact. This clearly implies that his STM is an impaired one while the LTM is intact. This certainly does not go in favour of the Dual Store model of memory.
Now, if we evaluate the second model i.e. the working model that it has also its own share of oppositions and support from various researchers and theorists. The support is mainly because the further lab research findings by Baddeley and Lewis in 1981 make it clear that articulatory – phonological loop indeed play a crucial role in silently rehearsing the words to remember its meaning as well as order within a sentence. To establish this fact, they presented some meaningful sentences with anomalies before their subjects and ask them to do comprehension and to spot the semantic anomalies existing within the sentences. The working model of memory comes into an existence mainly because of the constant criticism of the dual –store mode. The working model of memory draws criticism as although it makes an absolute sense to explain that diverse form of information are processed by various systems or memory units, it fails to accurately explain the function of long term memory as well as the functioning of central executive and visuo-spatial sketch pad. “The central executive is thought to play an important role in the control of attention, although it is becoming clear that attention control is not a unitary function, and the central executive is not the only system to contribute” (Miyake and Shah, p. 31). In fact, “the central executive is arguably the least theoretically developed” (Andrade 2001, p. 135) and thus the model still have a lot of scope for further improvement by research work.
There are many theories of forgetting and among those the comparison between the two major theories i.e. Trace Decay theory and the Interference theory is presented here. “Major theories of forgetting support the notion that forgetting is simply not being able to bring information to the conscious level when needed” (Taylor & MacKenney 2008, p. 211). The Trace Decay theory suggests that fading of the memory trace automatically led to forgetting over a course of time. This implies that “With the passage of time through disuse, these memory traces of learning impressions get weaker and weaker and finally fade away” (Mangal 1998, p. 215). This directly suggests that as we grow old, we forget all the more with passage of time. For example, many elederly person start forgetting small things frequently like whether they have locked the door or not, where they have kept their car keys or glasses, etc.
The Interference theory on the other hand states that interference is responsible for forgetting i.e. the things that we learnt recently interfere with the things that we learnt in the past and the interfering effect in turn led to subsequent forgetting. “Interference theory states that forgetting occurs because similar memories interfere with the storage or retrieval of information. Interference is an active theory of forgetting, without interfering events there is no forgetting” (Roeckelein, p. 318). The interference theory can be better understood by the following example - A woman proficient in classical form of dancing start learning salsa for a period of six months and after the completion of her course find it difficult to perform the intricate steps of classical dancing with same grace and poise as before. The main problem here is the interference of the new learning (salsa lessons) with the old one (classican lessons) stored in her long term memory unit.
Thus, the interference theory is in stark contrast with the trace decay theory where forgetting is explained as a result of gradual fading and not any displacement due to any new learning or information. The interference theory also suggests that encoded information can be affected by two types of interference in our memory-proactive and retroactive interference whereas in case of trace decay theory, the entire cause of forgetting is on the length of the interval time of rehearsal. In fact, many researchers have already rejected the trace decay theory of forgetting as an incorrect one.
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