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Cognition Human Factors Psychology Dr. Steve
CENTRAL PROCESSING PERCEPTUAL ENCODING RESPONDING ATTENTION RESOURCES Sensory Register Perception Response Selection Response Execution -Thought -Decision Making Working Memory Long-Term Memory Feedback Human Information Processing Model
Sensory Register • Information must first be picked up by the senses before it can be processed (e.g., visual, auditory, touch, taste, smell) • Sensory store holds large capacity of info • Information is maintained in sensory register for no more than 2 – 3 seconds (echoic) High Medium Low Sperling experiment demonstrates that info processed in sensory register is large, but short-lived
Subliminal Perception What images do you see in this glass? • Subliminal perception – perception below the threshold of awareness • Is it possible? • if so, how would it affect behavior? • Priming Effect – People can identify a stimulus faster the second time they see it, even if they weren’t consciously aware they saw it the first time.
Object & Pattern Perception • Perceptual Recognition – comparing incoming stimulus information with stored knowledge in order categorize the information. • Perception by feature analysis • Simultaneous top-down, bottom-up • processing Experts recall larger chunks of information (more chess pieces) when they recognize a meaningful pattern. When the pattern is random, performance same as novices.
Feature Analysis • Feature Analysis – recognizing and evaluating pattern features • Break stimulus pattern into component features • Match features to stored patterns in LTM • Decide which stored pattern is best match. • Unitization – transformation from feature analysis to global or holistic processing (Gestalt) as familiarity with pattern increases. • - allows us to read familiar words rapidly and overlook typographical errors. A
Feature Analysis HF Implications for Text Perception • Feature Compatibility – Features of display can be read faster and more accurately if they are consistent with features in memory • Upper and Lowercase – Printed CAPS are recognized more easily than lowercase in isolated words, but mixture of lower and upper cases is best for sentences • Example: WARNING!Keep a safe distance • Use print for text display – Print is easier to read than cursive • Minimize abbreviations – Avoid abbreviations, but when needed use a consistent rule such as 3 – 4 letter truncation. • Example: NAVAIRWARCENTRASYSDIV • Space between wordsor strings – separating strings into chunks makes it easier to read and remember • Example: (850) 555-1234
Feature Analysis Object Perception • Geons (Biederman) – fundamental geometric shapes that are combined to produce all other complex objects • We recognize an object by: • Breaking object into geons • Categorizing each geon on basis of feature match • Identifying the object on basis of geon configuration From a human factors perspective, what are the implications for simulator fidelity? - computer graphics vs. photo-realism
Top-down & Bottom-up Processing • Bottom-up processing (data-driven) – object recognition guided by sensory features • Top-down processing (conceptually-driven) – object recognition affected by surrounding context • Typically both processes work simultaneously, but when stimulus quality is low, top-down processing is predominant.
Top-down & Bottom-up ProcessingGuidelines for text and icon design • Optimize bottom-up processing • Ease of viewing and discrimination - size, contrast. • Optimize top-down processing • Use actual words, not random text strings • Minimize number of words that need to be recognized • Provide context information • Evaluate tradeoffs • Given limited space weigh importance of optimal viewing conditions vs. availability of context • Usability testing • When testing for usability DO include context in which stimulus will actually be seen
Visuospatial sketchpad Central executive Phonological loop Working Memory Baddeley’s model of working memory • Working Memory (short-term memory) – temporary (approx 30 – 90 sec) and limited capacity (7 +/- 2 chunks) of verbal and spatial information that is currently being used. • Info will be replaced by new info if not rehearsed. • Central Executive – attentional control system that coordinates info from other two subsystems. • Visuospatial Sketchpad – holds info in an analog • spatial form while it is being used. • Mental imagery • Phonological Loop – represents verbal information in an acoustical form while it is being rehearsed. • Sub-vocal articulation
*Vandenberg & Kuse Which two of the four shapes below are the same as this one? a. b. c. d. Spatial Ability As you try to answer this question, how is the central executive allocating your attentional resources?
Human Factors Implications of Working Memory Limits • Minimize working memory load • Keep the memory requirement short and small enough for WM • Provide visual echoes • Hard copy is not subject to decay • Exploit chunking • Physical chunk size – keep to 3 to 4 characters • Meaningful sequences – 1776/230/1492/755 • Superiority of letters over numbers – 1-800-ask-help • Keeping numbers separate from letters – HZY 701 • Minimize confusability • Create visual, audio, or spatial distinctions • Exploit different working-memory codes • Verbal info interferes more with other verbal info than with spatial info • Ordering of text and instructions • Order instructions congruently with order in which task accomplished
Long-Term Memory Long-Term Memory – Nearly permanent storage of information with unlimited capacity Encoding – placing info into memory Storage – keeping info in memory Retrieval – accessing information from LTM back into WM
Forgetting • Forgetting – caused by decay, interference, or inability to access (retrieve) information. • Memory retrieval fails due to: • Weak item strength due to low frequency or recency of reactivation • Ex: Password that is accessed once a semester • Weak or few associations of item with other info • Ex: (apple – red – fire – water) • Interfering associations • Ex: giving your current spouse an anniversary card on the anniversary of your previous marriage.
Organization of info in LTM • Semantic Networks – information is stored in a network of associations • Think about how you try to recall a name from your past. Does it start by thinking of something associated with that person? Which question is answered more readily: A: Are canaries yellow? B: Do canaries have skin? • Schema – One’s entire knowledge structure about a given topic • Experts knowledge may be structured very differently from novices • Mental Models – They way in which one expects a system to work. • Population Stereotype – similar mental models held by many people. • ex: light switch is on in up position, hot water knob is on the left
LTM implications for design • Problems • Consumers typically do not possess complete mental model of system • Owner’s manuals typically not clear and concise • Consumers do not want to refer back to manual at each use • Example: After recognizing the difficulty South Florida voters were having with their ballots, the following instructions were issued: “Attention all poll workers. Please remind all voters coming in that they are to vote only for one (1) presidential candidate and that they are to punch the hole next to the arrow next to the number next to the candidate they wish to vote for. Thank you!”
LTM implications for design • Design Solutions • Encourage regular use of information • this will improve frequency and recency for ease of recall • Standardize • Lessens amount of learning required when using new system • Ex: where is the wiper function control located in your car? • Use memory aids • Software menus provide info visible in sensory store, whereas command code must be retrieved from LTM • Carefully design information to be remembered • Info should be meaningful, concrete, distinctive, organized, free of jargon, presented in multiple modes, not require obscure context info • Encourage active verbalization • Design info to be consistent with user stereotypes • Design to support development of mental models • Input options and system state should be clearly visible
Declarative & Procedural Knowledge NOVICE Declarative Knowledge – (What) concepts, facts, principles, rules, mental models - gained quickly, decays rapidly - ex: rules of the road Procedural Knowledge – (How) implicit knowledge of how to perform a skill - takes longer to acquire, fades slowly - ex: driving EXPERT
Event Memory: Episodic & Prospective • Episodic Memory – personal knowledge or memory of a specific event (flashbulb) • Biased by plausible scenarios • Confidence in memory accuracy unrelated to actual accuracy • Implications for eyewitness testimony • ex:If you saw the events of 9/11 on TV, what did you see live and what did you see replayed? • Prospective Memory – memory of what one is supposed to do • Inability to retrieve info is referred to as cognitive failures or absent-mindedness • Failures prevented with reminders or checklists • ex: Sticky-note “to do” lists To Do:
Attention Due to limited attentional resources, humans must allocate attention appropriately Selective Attention – allows us to process important information - ex: “cocktail party effect” Focused Attention – allows us to filter out unwanted information - ex: studying with the radio on Divided Attention – allows us to perform multiple tasks at once - ex: driving while tuning the stereo Time-Sharing – switching between cognitive tasks - results in “time-sharing decrement” – the drop in performance of one or both tasks HF implication: how is driving affected by cell phone use?
Automatic vs. Controlled Processing Controlled Processing – effortful cognitive processes requiring attention to initiate and sustain (processing unfamiliar info) Automatic Processing – processing performed with little demand on attention (well practiced tasks) Blue Red Green Yellow Green Red Yellow Blue Red Yellow Green Blue Yellow Green BlueRed Green BlueRedYellow Stroop Effect
Attentional Resources Allocation • Easiest to time-share limited resources when the two tasks: • Differ in terms of whether the info is processed early (e.g., perception) and late (e.g., response selection) stages • Require different input modalities (visual vs auditory) • Differ in terms of input to response coding (verbal/vocal vs visual/manual) VERBAL SPATIAL