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Lecture 12

Lecture 12 Memory Detailed Note.docx

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1 Psychology Lecture 12: Memory Bernard Ho November 2, 2010 Introduction to Memory  Memory metaphors o Video camera that accurately preserves images and audio to be played back at a later time o Filing cabinet in which memory files are stored in an organized folder system, which can be accessed to remember something o Computer with specialized components responsible for handling different memories at different times  Noted psychologist Frederic Bartlett realized that all these metaphors about human memory have something in common o Each assumes that memory can store experiences in their original, undistorted form (stored and retrieved data is identical to inputted information) o Each also assumes that memory retrieval is as simple as accessing a previously stored item that has been kept in a specific place The Basics of Memory  Psychologists have generally asked three types of questions about memory o Memory acquisition  What will be stored in memory?  Encoding reflects data entry or how information initially enters into memory, a selective process that is highly dependent on attention o Memory storage  How and where will it be stored?  Concerns how the record of memory is maintained over time  This record is not fixed and can be modified o Memory retrieval  How can memories be returned to consciousness  Dependent on retrieval cues, key pieces of information that has the potential to activate a memory in full  In a sense, like the cue-response mechanisms studied by behaviourists, one memory acts as a cue to trigger another memory  Early researchers of memory were heavily influenced by behaviourists so early focus of memory research concerned how cues interact with encoding and retrieval mechanisms of memory  Hermann Ebbinghaus o Brought controlled conditions of the lab to study memory o Operationally defined memory as a serial learning task 2 o As Ebbinghaus memorized word lists, he suggested that each word in the list served as a cue that triggered the memory of the word that followed o Each word connects to the word before and after it  Psychologists rely on cognitive models to understand a complex cognitive function like memory  Models describe and organize data and most importantly, make specific testable predictions that can be studied in controlled experiments in the lab  The basic memory task involves two phases o During the encoding phase, a subject learns a list of items, words or pictures o During the retrieval phase, subjects are tested for their memory of the items presented in the encoding phase  During a recall test, a subject is asked to freely generate as many items as they can remember  During a recognition test, a subject is shown several items and asked to judge whether each item is “new”, meaning it was not presented during the encoding phase or “old”, meaning the item was presented during the encoding phase  Ebbinghaus used the basic encoding and retrieval design to learn about cueing and forgetting of memories  Using himself as a subject, he memorized lists of “nonsense words” during the encoding phase and later tested his recall ability during the retrieval phase  Importantly, Ebbinghaus chose to use nonsense words to minimize the influence of his prior experience on his test results  One of the research questions that interested Ebbinghaus was how long memories could be maintained  He found that his ability to recall words was highest immediately following learning and that over time he was able to remember fewer and fewer words  From these observations, Ebbinghaus constructed the forgetting curve, which describes this increasing rate of memory failure over time The Multi-Store Model  Model proposed by Atkinson and Shiffrin  The multi-store model assumes that memory is composed of three separate stores, sensory, short and long term storage systems  Sensory memory o The transient maintenance of perceptual and physical information from the very recent past o Ex. Looking around an environment, your eyes move across the scene, stopping for brief intervals to gather information o Although this is the same as taking snapshots at different locations, you perceive the world as a continuous representation o This is because each snapshot is briefly maintained and then replaced by the next o All your senses maintain a similar transient memory representation 3 o Iconic memory for visual information is represented by the visual system, whereas echoic memory for auditory information is represented by the auditory system o Sensory representations are displaced or overwritten by new incoming information o Sperling tested the longevity of sensory memories in the absence of displacement by briefly (50 ms) presenting arrays of three rows of three numbers o Participants viewed the arrays and then listened for a tone of high, medium or low pitch to indicate which row to report o Despite the brief presentation time, if the tone sounded immediately after the array presented, participants were surprisingly accurate at reporting the numbers o However, if the tone sounded just one second later, they recalled nothing, illustrating the extremely fast rate at which sensory memory decays  Short term (working) memory o Information that is selected from sensory memory enters consciousness and is maintained in the short term or working memory buffer o Short-term memory holds selected information for a short period of time, but not necessarily stored permanently o If unrehearsed, selected information can be maintained in the short term memory buffer for about 20 seconds o If items in short-term memory are rehearsed, they may become transferred into the long-term memory store o Miller demonstrated that for most short-term memory tasks, people can remember about 7 plus or minus 2 items o Any more than that and the demand on short term memory becomes strained o If rote rehearsal stops, the short term memory can fade o Chunking  Miller discovered that people can re-organize or “chunk” information in meaningful packets, allowing more information to be held in short-term memory  Letter groupings that form words pack even more information into a single chunk  Ex. You may only be able to remember 7 random letters, but you can also remember 7 different animals even though all these names contain several letters each  Chunking can even be applied to more complex visual information  If a chess expert and a novice are briefly shown a chessboard with pieces placed at random and later asked to recall the position of the pieces, both are likely make several errors  However, if the expert and novice are briefly shown a chessboard with pieces placed from an actual game, the expert is likely to 4 have an upper hand when asked to recall the position of the pieces o Working memory can be thought of as an upgrade to the original conceptualization of short-term memory  Consists of three short-term stores  Phonological loop o Encapsulates the original notion of short-term memory ( a temporary online store that can maintain seven plus or minus two bits of phonological information for some time) o Maintains information that can be rehearsed verbally o Ex. Is engaged when rehearsing the number of a store  Visuospatial sketchpad o Thought to temporarily represent and manipulate visual information o Ex. Is engaged when trying to remember a mental map of how to get to a store  Episodic buffer o Thought to draw on other buffers as well as on other stored long-term memories o Engaged when remembering specific past episodes  In addition to the multiple buffers, working memory model includes a central executive, which coordinates and manipulates information that is temporarily maintained in the buffers  Central executive allows working memory to be much more flexible and controllable than short-term memory was originally conceived  Long term memory o Thought to be stored permanently o According to multi-store model, information can be copied from short-term memory to long-term memory, but this transfer is largely dependent on rehearsal of that information o Once in long-term memory, new information seems to be organized according to prior knowledge o We have a tendency to recall related information in clusters or groups, even if that information was learned in random order o Flow of information between short-term and long-term stores is not unidirectional o Information is also transferred from a stored state into a conscious state (long term to short term) o Effectively what happens when we are remembering the past o Long term memory storage system can be subdivided into separate systems based on the type of information stored o Declarative memories  Ex. Memory for factual information, explicit memories  Example of the prototypical conception of memory 5  Information could include general knowledge or semantic memories that are not tied to a particular place or time (roses are red)  Can also include specific memories of past personal experiences or episodic memories that are tied to a particular place or time (I remember how red those roses were) o Nondeclarative memories  Ex. Learned actions, skills, conditioned responses, implicit memories  Memories that are hard to articulate  Ex. You know how to ride a bike, but you would have difficulty describing how you do so (procedural) The Serial Position Curve  Memory performance is often best for items early or later in the list and worst for items in the middle  This pattern of performance is summarized in the serial position curve  Primacy Effect o Memory performance is good for items encoded early in the list o According to the multi-store model, the items at the beginning of the list will be the first to enter short-term memory and thus have the most opportunity to be rehearsed o As a result of rehearsal, memory performance for the early items is good because they have entered long term memory o By comparison, items in the middle of the list have less opportunity for rehearsal and thus, have less opportunity of being transferred into long-term memory o Consequently, memory performance for these middle list items suffers  Recency Effect o Memory performance is good for items encoded latest in the list o Since you can only hold around 7 items in short-term memory, as you progress through the list, the newest items replace the oldest items in the short-term memory buffer o However, as you reach the end of the list, the last 7 or so items are not replaced by new items and will remain in short term memory o As a result, memory performance will be good for the last few items because they are still active in the short-term memory storage system  If the primacy effect is driven by rehearsing items into the long-term memory, then the primacy effect should be influenced by a manipulation that changes a subject’s ability to rehearse items o Can be tested by manipulating the presentation time of each to-be-remembered item o Presumably, more time to encode each item would also allow more time for rehearsing those items into long-term memory 6 o As a result, the primacy effect should be enhanced for a list of items given with a long interval of presentation relative to a list of items given with a short interval of presentation o Increasing time between item presentations increases  Amount of times each item can be repeated  Probability of item being stored in long term memory  Performance recalling first couple of items  If the recency effect is driven by items remaining active in the short-term memory buffer, then it should be influenced by any manipulation that affects the contents of the short term memory store o Ex. A manipulation that causes the most recent contents of the short-term memory to be replaced or disrupted should neutralize the recency effect o Could be tested by asking a subject to perform a distracting task immediately following the encoding phase o Performing a distracting task would require short-term memory resources, causing the last of the to-be-remembered items to be disrupted from being active in the short term buffer o Consider an experiment in which three groups of subjects are used  The first group is asked to memorize the list of items, then performed a distracting task for 30 seconds before recalling the list  The second group is asked to memorize the list of items, then simply wait 30 seconds before recalling the list  The third group is asked to memorize the list of items and immediately recall the list with no delay o As expected, the recency effect disappears only for the first group, but was maintained for the control group The Levels of Processing Model  Proposed by Craik and Lockhart and suggests that memory performance depends on the level at which items are encoded  An item encoded at a Shallow level requires little effort and is often directed at the physical characteristics of a stimulus o As a result, memory performance is poor  An item encoded at a Deeper level requires more effort and is often directed at the semantic or meaning-based characteristics of a stimulus o As a result, memory performance is richer  In a clever experiment, Craik and Lockhart tested the levels of pro
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