Lecture 5 (STWM).ppt

Short-Term Working Memory Lecture 5 Aspects of STM • Where the immediately present moment is held in consciousness. • Where active mental effort is expended. • Where comprehension takes place. Synonyms for Short Term Memory • Working Memory; Intermediate Memory; Elementary Memory; Short-term Stor...

Short-Term Working Memory Lecture 5 Aspects of STM • Where the immediately present moment is held in consciousness. • Where active mental effort is expended. • Where comprehension takes place. Synonyms for Short Term Memory • Working Memory; Intermediate Memory; Elementary Memory; Short-term Store; Temporary Memory; Primary Memory. Short Term Versus Working Memory • STM: Older term emphasizing input and storage of new information (e.g., a phone number). • Working Memory: Newer term emphasizing processing and storage – the mental workbench. Short Term Memory: A Limited Capacity Bottleneck • Miller’s Magical Number Seven, Plus or Minus Two. • Overcoming the bottleneck: Chunking – grouping individual items into a richer, more complex item. Recoding – the act of grouping items together, then remembering the newly formed groups. Mnemonic Devices – a rehearsal or recoding strategy (e.g., method of loci). The Brown-Peterson Task • Research Aim: Determine how long nonrehearsed information stays in STM. • On each trial, the subject sees three letters, followed by three numbers: e.g., PIR-393. • Subjects must remember the letters while counting backwards by 3’s from the number. • Plot recall accuracy by time spent counting. Recall Accuracy in the Brown-Peterson Task Brown-Peterson’s Interpretation. • The data represent a simple decay function. • Decay (or fading): Loss of a memory trace due simply to the passage of time. • Interference: (loss of a memory trace due to competition from other events) plays little or no part in this task. Challenges to BrownPeterson • Waugh and Norman (1965) • Subjects heard a list of 16 digits read at either 1 or 4 digits per second. • Last digit was a repeat of an earlier one. Subject had to remember which digit came after it in the list. • Example: 7, 4, 6, 9….4….. Waugh and Norman’s Predictions • Decay Hypothesis: predicts greater rates of forgetting in the 1/sec condition than in the 4/sec condition. WHY? • Interference Hypothesis: predicts similar recall curves for both conditions. WHY? Waugh and Norman’s Results • There was very little difference in the recall curves of the 1 and 4/second groups • How do Waugh and Norman’s results demonstrate that interference rather than decay is the loss mechanism in STM? Further Evidence of Interference • Keppel and Underwood (1962) Performance on the Brown-Peterson Task is relatively good early on (and nearly perfect on Trial 1). Performance gets much worse on later trials. How is this evidence for interference? Proactive Versus Retroactive Interference • PI:Previously presented material interferes with new learning (e.g., walking today to where you parked your car yesterday). • RI:Recent material interferes with older learning (a busy signal erases memory of a phone number) Release from PI in the Brown-Peterson Task • • • • • • • Wickens (1972) Do these sample trials: Dog, Cat, Mouse: 745 Rabbit, Horse, Tiger: 687 Elephant, Zebra, Lion: 496 Cow, Bear, Wolf: 313 Doctor, Lawyer, Baker: 891 Release! Release from PI in the Brown-Peterson Task Short-Term Memory and Recall • Types of Recall • Free: Recall the items in any order (e.g., a grocery list). • Serial: Recall the items in exact order of presentation (e.g., a phone number). Serial Position Effects • Primacy: Better memory for the first items in a list. • Recency: Better memory for the last items in a list. The Serial Position Curve Standard Explanations • Primacy Effects: A long-term memory effect. First items in a list get the best and most rehearsal. • Recency Effects: A short-term memory effect. Last items still in STM at time of recall. Evidence for the Standard Explanation • Glanzer and Cunitz (1966) • Distractor task wipes out the recency effect, but not the primacy effect. • Why should this occur? Two Properties of Rehearsal • Keeps information in STM. • Increases probability information will be transferred to long-term memory. Sternberg’s (1966) Methodological Advance • Donders subtractive logic: Task 1 = components A + B + C = RT1 Task 2 = components A + C = RT2 B = RT1-RT2 • Sternberg argued that one could not be sure that the process components A and C were not simplified. • Sternberg figured that if you wanted to study process B, you had to examine process B when the process was repeated one to several times per trial. Sternberg’s (1966) STM Scanning Task • How do we search the contents of STM? • On each trial, subjects saw a memory set, consisting of between 2 and 5 letters. • After the memory set disappeared, a single, probe digit appeared. • Yes or No, was the probe digit a member of the memory set? Sample Sternberg Task Process Model of the Sternberg Task How Might People Scan STM? • Parallel Search (e.g., yes, or no, are my car keys on the table?). • Serial self-terminating search (e.g., my keys could be on the sofa, the kitchen table, or in the car. I find them on the sofa, and stop my search). • Serial exhaustive search (e.g., a police line up). Sternberg’s Results Summary of Sternberg • The intercept represents the time it takes for all other stages in Sternberg’s model. • People scan STM in a serial exhaustive fashion (don’t stop even if a match is found). • The scan rate is about 38 msec per item (Sternberg’s slope). Multiple Codes in STM • • • • Verbal Codes (Conrad, 1964) Semantic Codes (Wickens, 1972) Visual Codes (Shepard & Metzler, 1971) Cherological Codes (Shand, 1982) Working Memory Working Memory Components of Working Memory • Central Executive: In charge of planning future actions, initiating retrieval and decision processes as necessary, and integrating information coming into the system. Components of Working Memory • Visuo-Spatial Sketch Pad One of Two Slave System. A system specialized for visual and spatial information. Example: Is the doorknob for your bedroom door on the left or right side? Components of Working Memory • Articulatory Loop The Second Slave System. The speech and sound related component responsible for rehearsal of verbal information and phonological processing. Components of Working Memory • Episodic Buffer Holds information that has been processed through articulation (Articulatory Loop), visualization (VSSP) and relevant LTM information to form a coherent scene or episode. Studying Working Memory • Dual Task Method • Examples: Working Memory and Reasoning. Working Memory and Language Comprehension. Working Memory and Visual Processing. Brooks (1968) Neuropsychological Evidence for Working Memory I Neuropsychological Evidence for Working Memory II Individual Differences and Working Memory • Engle’s (2000) Memory Span Tasks. • Require simultaneous mental processing and storage of information in working memory. • Performance on these tasks correlate strongly with aptitude and achievement tests.