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Chapter 6

PSY342 - chapter 6 notes

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University of Toronto St. George
Ari Silburt

Chapter 6- Working Memory • We need to keep some bits of information accessible in mind to perform cognitive operations of them, mull them over and transform them. This short term mental storage and manipulation operations are collectively called working memory • Working memory is similar to a blackboard that temporarily holds information and allows us to alter it, but once we are done with the information it can be erased Computer Metaphor • Working memory is analogous to computer’s RAM, but comparison with RAM leads to two further predictions: 1. Any program can access RAM, therefore, no fixed mapping of a part and its related processes 2. As there is more RAM, we can multi-task more Implications of the Nature of Working Memory • Working memory capacity; the amount of information that can be held accessible. People vary in their working memory capacity and this variation accounts for the differences in intelligence, learning etc From Primary Memory to Working Memory: A Brief History William James: Primary Memory, Secondary Memory, and Consciousness • Primary memory is the initial repository in which information can be stored and made available to conscious inspection, attention and introspection. In this way, information is continually accessinlr • Secondary memory/long term storage memory is the store from which information cannot be retrieved without initiating an active cognitive process Early Studies: The Characteristics of Short-Term Memory • Miller suggested that people can only keep 7 items active in the short-term storage and this limitation influences performance on a wide range of mental tasks. This concept was supported by the tests of short-term memorization • The short term memory is perceived as highly flexible and subject to manipulation • Single items can be grouped together into higher level units of organization called chunks; that expand the capacity of short term memory. Chunking is governed by by concept of meaningfulness • Words are put into phrase-chunks which is why it is easier for us to remember verbal information • Recent research suggests that number of items held in the memory may just be 3 +/- 1 because if participants are prevented from chunking/rehearsing, the storage capacity is perceived as much smaller • Short term memory is defined in terms of its short duration and high level of accessibility Brevity of Duration • The idea is that information would be held in the short-term memory for a very brief period of time if the participants are not allowed to rehearse the information. • This idea has been supported by the results of Brown-Peterson task; where accuracy declines by 50% in the first 6 seconds and to 0 after 18 seconds • Investigations are also being made about sensory memory; a form of storage that serve to keep a perceptual representation of a stimulus for only a few 100 milliseconds after the sensory input is gone • For short term memory, it has been observed that forgetting is not because of passive decay over time but because of the idea of interference Ready Accessibility • Sternberg’s experiment: Participants were showed a list of digits and then after showed a digit and were asked to make the judgment about whether or not the digit was in the memory list. 4 things were measured: 1. The time required to process the stimulus 2. The time required to access and compare the items 3. The time required to make the stimulus-response decision 4. The time required to execute the motor decision • It was noticed that for each additional item added in the memory list, response time increases by an average of 40 milliseconds • This task also leads us to the conclusion that memory scanning proceeds sequentially; one at a time. However, processing may be parallel The Atkinson-Shiffrin Model: The Relationship of Short-Term and Long-Term Memory • The Atkinson-Shiffrin Model: In this model, short-term memory serves as the gateway by which information gains access to long-term memory. Short-term memory provides a means of controlling and enhancing via rehearsal and coding strategies which lets the information enter into long-term memory • This model had a lot of support and was called the modal model but is no longer held that strongly because working memory captures the idea better where information is held for manipulation • Argument against the Atkinson-Shiffrin Model is that it emphasized the role of sequence; information first comes into the short term memory and then enters the long- term memory but people with short-term memory impairment can hold information in the long term memory very well. • There are multiple systems available for short-term storage that are co-ordinated by central control system that balances the processing and storage The Baddeley-Hitch Model: Working Memory • A system that consists of two short-term stores and a control system. • Three characteristics that differentiate this model from the Atkinson-Shiffrin Model: 1. It does not state that the function of short-term memory is to provide route for the information to the long-term memory but the function is to enable the activities of cognition e.g. co-ordination, integration and manipulation 2. Emphasizes the relationship of a central executive; a control system that governs the deposition and removal of information from short-term memory. Allows the short-term memory to function optimally 3. It proposed two distinct short-term memory buffers; phonological loop which is for verbal information and visuospatial scratchpad which is visuospatial information. The two memory stores are independent of each other as in if one is being used, the other can be optimally used as well. They both interact with central executive for functioning • Baddeley-Hitch model does not emphasize the duration of short-term memory or its relation to long term memory. Rather, it emphasizes its flexibility and its importance in the manipulation of information Understanding the Working Memory Model The Phonological Loop • The phonological loop involves two subcomponents: 1. Articulatory rehearsal: When visually presented verbal information is encoded, it is transformed into a sound-based code or auditory-phonological code, the active refreshment comes from articulatory rehearsal where we voice the sounds internally – shadow the words without real understanding 2. Phonological store: Once the information is rehearsed in the mind, then it can be heard again by the mind’s ear and maintained in the phonological store • Working memory depends on level of phonological processing i.e. translating verbal information into sound-based code and articulatory processing i.e. translating verbal information into speech-based code • If for some reason, phonological loop stops working, one can always use the visuospatial scratchpad e.g. you cannot internally speak your ideas because you are listening to someone else talk then you start to visually write your idea • Phonological similarity effect; when items simultaneously stored in working memory have to be serially recalled then performance is worse for phonologically similar words. The effect is believed to be because similar sound-based codes are activated for different items • Word length effect; this operates within the articulatory rehearsal. Performance is worse for words that take longer to pronounce. • If phonological loop stops working, we use the visuospatial scratchpad. The idea is supported by dual-interference task in which articulatory suppression occurs because people are asked to talk and hold the words in memory • Cortical regions are believed to be involved in language processing • It was observed that patients with damage to the cortical areas have special difficulty with auditory verbal working memory because the auditorily presented information needs to be first processed phonologically before you can use the visuospatial scratchpad. Therefore, scratchpad does not help • However, if the information is presented visually then there is not that difficulty, because one can switch to the scratchpad without engaging in the phonological loop. • In such cases, phonological effect can be observed because one still says the words outloud but word effect is not observed because one does not need to articulate the words within the mind • The phonological store relies particularly on left interior parietal cortex • The articulatory rehearsal relies particularly on left interior frontal cortex -(Broca’s area) – dorsal area with initial articulation, ventral with repeated rehearsal • Also, if word length and phonological similarity are two independent componen
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