Short-Term & Working Memory PDF

Memory: the processes involved in retaining, retrieving, and using information about stimuli, images, events, ideas, and skills after the original information is no longer present just about everything we do depends on remembering what we have experienced in the past Mental representations: t...

Memory: the processes involved in retaining, retrieving, and using information about stimuli, images, events, ideas, and skills after the original information is no longer present just about everything we do depends on remembering what we have experienced in the past Mental representations: the elements of memory systems Many types of codes: semantic, acoustic, visual, etc. Mental processes: mechanisms for accessing “old” knowledge, encoding new information, keeping information “alive” STUDYING MEMORY ATKINSON & SHIFFRIN’S MODAL MODEL OF MEMORY The stages in the model are the structural features of the model: 1. Sensory memory is an initial stage that holds all incoming information for seconds or fractions of a second 2. Short-term memory (STM) holds 5–7 items for about 15–30 seconds 3. Long-term memory (LTM) can hold a large amount of information for years or even decades Memory systems include control processes, which are active processes that can be controlled by the person and may differ from one task to another Ex: rehearsal: repeating a stimulus over and over strategies you might use to help make a stimulus more memorable strategies of attention that help you focus on information that is particularly important or interesting Encoding: process of storing the stimulus in long-term memory Retrieval: process of remembering information that is stored in long-term memory Memory disruption: inability to store or retrieve the information Storage failure: permanent failure Retrieval failure: temporary amnesia SENSORY MEMORY Sensory memory: the retention, for brief periods of time, of the effects of sensory stimulation Encodes features from the environment Is modality-specific (visual, acoustic, tactile, olfactory, gustatory) is short-lasting THE SPARKLER’S TRAIL AND THE PROJECTOR’S SHUTTER Persistence of vision: retention of the perception of light in your mind If the period between the images is too long, the mind can’t fill in the darkness completely, and the intensity of the image appears to flicker SPERLING’S: MEASURING THE CAPACITY AND DURATION OF THE SENSORY STORE how much information people can take in from briefly presented stimuli Experiment 1: whole report method: participants were asked to report as many letters as possible from the whole matrix Results: Reported an average of 4.5 out of the 12 letters Experiment 2: partial report method: flashed the matrix for 50 ms, + cue tones, to indicate which row of letters the participants were to report Results: correctly reported an average of about 3.3 of the 4 letters You encode all or almost all the information for a very short period of time Experiment 3: delayed partial report method: presentation of cue tones was delayed for a fraction of a second after the letters were extinguished Results: participants were able to report only slightly more than 1 letter in a row Iconic memory: immediately after a stimulus is presented, all or most of the stimulus is available for perception and over the next second, sensory memory fades until 1 sec Echoic memory: persistence of sound in the mind, which lasts for a few seconds after presentation of the original stimulus Sensory store is important for collecting information to be processed holding the information briefly while initial processing is going on filling in the blanks when stimulation is intermittent SHORT-TERM MEMORY Information either reaches STM or is discarded Short-term memory (STM): the system involved in storing small amounts of information for a brief period of time Everything we think about or know at a particular moment in time WHAT IS THE DURATION OF STM? Retention and Forgetting Recall test: participants are presented with stimuli (3 consonants) and then, after a delay, are asked to remember as many of the stimuli as possible Memory performance is measured as a percentage of the stimuli that are remembered If there is a pattern to the way items are recalled Results: Decay: memory trace decreases over time memory becomes worse as time interval increases (longer distractor task) Proactive interference (PI): interference that occurs when information that was learned previously interferes with learning new information Ex: when a frequently used phone number is changed & when new number is similar to the old one adds to the interference HOW MUCH INFORMATION CAN STM HOLD? Digit Span: the number of digits a person can remember measure of the capacity of STM typical span is ~ 7+/- 2 Relies on individual differences and prior knowledge Attention plays a role Chunking: grouping process in which small units (like words) can be combined into larger meaningful units, like phrases, or even larger units, like sentences, paragraphs, or stories chunk: a collection of elements that are strongly associated with one another but are weakly associated with elements in other chunks Grouping information relies on meaningful codes (categorization) Semantic in nature MEMORY AND ATTENTION WORK TOGETHER need attention to put together the appropriate codes that yield chunks Attention is required for keeping (the right sort of) memory codes alive need principles/rules for chunking the right kind of info together Chess Experiment The easiest and fastest way to remember the pieces’ location is to group together to same pieces (chunking) Expertise aids chunking for actual board positions But when pieces are randomly placed, experts struggle more than beginners to chunk pieces together HOW IS INFORMATION CODED IN STM? Coding: the way information is represented physiological approach to coding: determining how a stimulus is represented by the firing of neurons mental approach to coding: determining how a stimulus or an experience is represented in the mind What are the codes of representation in STM (Conrad) PART 1: Visual (saw letters) With telephonist: good at acoustic each letter appeared for 5ms After 6 letters subjects were asked to write down what they had seen Results: Increased errors for letters that sound the same deaf subjects show the same pattern of errors (based on phonological properties) PART 2: Auditory (heard letters) With postal workers: good at visual one letter every 5 seconds and wrote down what they thought they heard after each letter Results: Increased errors for letters that sound the same (not looked the same) Auditory coding involves representing items in STM based on their sound most likely to misidentify the target letter as another letter that sounded like the target “F” most often misidentified as “S” or “X” (sound similar) “F” was not as likely to be confused with letters like “E” (look similar) Visual coding involves representing items visually when remembering the details of a floor plan or the layout of streets on a map participants were able to complete patterns consisting of an average of 9 shaded squares before making mistakes Release from Proactive Interference Semantic coding is representing items in terms of their meaning Induce proactive interference (the decrease in memory that occurs due to prior learning) interference can be attributed to the meanings of the words Varies with the type of stimuli Results: Recall decays if new trial has items from the same category Proactive interference Recall improves if items are from new category Release of proactive information STM codes (representations) are also semantic When dealing with many representations of the same kind, they interfere with each other WORKING MEMORY Memorizing involves transferring the number from STM into LTM Remembering involves transferring it from LTM back into STM ENCODING & LEVELS OF PROCESSING Depth of processing: “greater ‘depth’ implies a greater degree of semantic or cognitive analysis Preliminary stages are concerned with the analysis of such physical or sensory features Later stages are more concerned with matching the input against stored abstractions from past learning later stages are concerned with pattern recognition and the extraction of meaning How long-lasting are the memory codes (Tulving) Subjects were presented with a list of words followed by recall; task: rate “physical” aspects: upper vs. lower case rate phonemic aspects: rhyming rate semantic aspects: sentence fit Results: Semantic processing that is encoded has longer traces Higher RT = increased depth of processing (better encoded) PROBLEMS WITH THE THEORY: Doesn’t specify the nature of the levels and how they differ from each other Different vs continuum Doesn‘t take into account encoding/retrieval matching situations Better recall when encoding and retrieval contexts match STM & MODAL MODEL NOT SUITED FOR STM Short-term processes are needed not only for storage, but also for active processes do not consider dynamic processes that unfold over time Under certain conditions it is possible to carry out two tasks simultaneously, as illustrated in the following demonstration Baddeley’s working memory model Working memory: a limited-capacity system for temporary storage and manipulation of information for complex tasks such as comprehension, learning, and reasoning differs from STM in 2 ways: 1. STMis concerned with storing information for a brief period of time, whereas WM is concerned with the manipulation of information that occurs during complex cognition 2. STM consists of a single component, whereas WM consists of a number of components MANIPULATION OF INFORMATION through the action of three components: 2 active (phonological loop and visuospatial sketchpad) and 1 controller (central executive Components are relatively independent: If 2 tasks use the same component, they can’t be performed successfully together If 2 tasks use different components, they should be able to be performed similarly together or separately 1. phonological loop: holds verbal and auditory information phonological store: has a limited capacity and holds information for only a few seconds articulatory rehearsal process: responsible for rehearsal that can keep items in the phonological store from decaying 2. visuospatial sketch pad: holds visual and spatial information 3. central executive: decide how to divide attention between different tasks phonological loop and the visuospatial sketch pad are attached where the major work of working memory occurs pulls information from long- term memory and coordinates the activity THE PHONOLOGICAL LOOP 3 phenomena that support the idea of a system specialized for language: Phonological similarity effect: the confusion of letters or words that sound similar occurs when words are processed in the phonological store part of the phonological loop Memory suffers for similar items because they are confused with one another Word length effect: when memory for lists of words is better for short words than for long words occurs because it takes longer to rehearse the long words and to produce them during recall Articulatory Suppression: occurs when a person is prevented from rehearsing items to be remembered by repeating an irrelevant sound (ex: “the, the, the…”) Caused by repetition of an irrelevant sound reduces memory because speaking interferes with rehearsal eliminating rehearsal by saying “the, the, the...” eliminates word length effect THE VISUOSPATIAL SKETCH PAD Visual imagery: the creation of visual images in the mind in the absence of a physical visual stimulus Mental rotation: rotating an image of one of the objects in the mind Tasks that have an increased amount of rotations take longer the visuospatial sketch pad can become overloaded and cause interference THE CENTRAL EXECUTIVE makes working memory “working” Attention controller: determines how attention is focused on a specific task, how it is divided between two tasks, and how it is switched between tasks Frontal lobe plays central lobe Damage can cause perseveration: repeatedly performing the same behaviour even if it is not achieving the desired goal THE EPISODIC BUFFER 2 PROBLEMS WITH BADDELEY’S MODEL 1. working memory can hold more than would be expected based on just the phonological loop or visuospatial sketch pad By chunking 2. there is an interchange of information between working memory and long-term memory SOLUTION: Episodic buffer: can store information (=extra capacity) and is connected to LTM (= making interchange between working memory and LTM possible)