The Estimation One Dominant Theory of Memory and the Amnesic Evidence Associated with the Model
People use their memory all day every day. Without memory, doing simple tasks such as talking, walking, and writing would be impossible. Learning how memory works is an important first step in understanding the multistore model. The first stage is encoding, also known as the input stage, where newly perceived information is transformed into a memory trace. Without rehearsal, this information will be forgotten. The second stage is storage where the information is then retained and held for future use. And the third and final stage is retrieval where extracting of information from storage occurs. In order to successfully retrieve a memory, each of the three stages must be completed. Forgetting can occur at all three stages but due to different reasons. Forgetting in the sensory store is due to decay as memories fade away with time, and if the information is not rehearsed, regardless of other input. Displacement occurs in the short-term memory (STM) where memories are actively disrupted by the influence of another input. There are two forms of displacement; proactive and retroactive. Proactive is where previous input affects current learning and retroactive interference is where future input affects current learning. Finally, forgetting in the Long-term memory (LTM) is due to the interference of retrieval which occurs when we have numerous memories associated with a cue, and we chose to rehearse only one or two of those memories. A final point to make about memory is that it is important to distinguish between architecture and processes, however, one must also remember that without architecture there is no process.
One model used to explain memory is Atkinson and Shiffrin’s multi-store model of memory, and within this model, there are 3 main components. The architecture of this memory system comprises a sensory store, an STM store, and an LTM store. These stores are places where information is located for varying periods of time, for example, information might be held for seconds in the STM stores but and minutes to a lifetime in the LTM store. The information entering the sensory store is modality-specific and is held only for a short time and if paid attention to, the information in the sensory store will be processed further into the STM. Atkinson and Shiffrin characterized the short-term store (STS) as having a limited capacity of around 4-7 items and so information can be easily lost due to decay. Finally, if the information in the STM was rehearsed then it would move on into the LTM where in comparison was characterized as having a large capacity.
Evidence supporting Atkinson and Shiffrin’s multi-store model comes largely from people suffering from amnesia. Amnesia is known as any disorder of memory and a pathological impairment of the function of memory. It involves severe forgetfulness, which goes beyond everyday forgetting observed in normal life situations, and can provide information and understanding of memory function. These amnesic syndromes help provide a classic distinction between STM and LTM memory in the multi-store model. Amnesia may arise from a number of aetiologies. The two main causes are organic amnesia which is caused by biological factors such as brain disorders, tumors, strokes, and degenerative diseases, and psychogenic amnesia which is caused by psychological factors, but no actual brain damage. Amnesic patients show a dissociation, where some have impaired LTM but intact STM. Dissociation between STM and LTM provides evidence that they are separate and independent memory stores.
One important case study looked at by Milner, Corkin & Teuber, 1968; Scoville,1954, is Harry Molaison, also known as H.M. H.M suffered from seizures when he was an adolescent due to epilepsy. Tests confirmed that seizures had begun in both temporal lobes resulting in a surgeon needing to remove the majority of the anterior lobes on both sides (bilateral mesial temporal lobectomy). The surgery relieved epilepsy however Henry had lost the ability to form new memories, known as anterograde amnesia. Henry could retain new information but only for a moment. When measuring his STM measured by digit span, tests showed that it is unimpaired as he held a span of 6 (average is 4-7). He however lost the ability to form new long-term memories meaning that he had intact STM but a damaged LTM.
According to Atkinson and Shiffrin, the multi-store model is sequential and so information can only enter LTM if it first passes through STM. However, there are case studies that show patients with impaired STM but intact LTM. One of these studies involves a patient known as K.F whom had a severe impaired STM due to a motorbike accident that led to brain damage in the left parieto-occipital lobe. Tests showed that his digit span was two, and if the test was repeated his performance would deteriorate, and so on occasions, his digit span would be 1 or even zero. This difficulty wasn’t just for digits, it also applied for both letters and words.
