CognitionCognition

Human Factors Human Factors PsychologyPsychology

Dr. SteveDr. Steve

Human Information Processing ModelHuman Information Processing Model

SensoryRegister

Perception

Long-Term Memory

WorkingMemory

-Thought-Decision Making

ATTENTIONRESOURCES

ResponseSelection

ResponseExecution

Feedback

PERCEPTUAL ENCODING

CENTRALPROCESSING RESPONDING

Sensory RegisterSensory 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)

FF WW BB QQ

RR YY UU CC

ZZ KK PP MM

High

Medium

Low

Sperling experiment demonstrates that info processed in sensory register is large, but short-lived

Subliminal PerceptionSubliminal Perception

Subliminal perceptionSubliminal 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.

What images do you see in this glass?

Object & Pattern PerceptionObject & Pattern Perception

Perceptual Recognition – comparing incoming stimulus information with stored knowledge in order categorize the information.

1. Perception by feature analysis2. 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 AnalysisFeature Analysis

Feature Analysis – recognizing and evaluating pattern features1. Break stimulus pattern into component features2. Match features to stored patterns in LTM3. 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 Feature Analysis HF Implications for Text PerceptionHF Implications for Text Perception1. Feature Compatibility – Features of display can be read faster and

more accurately if they are consistent with features in memory 2. 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

3. Use print for text display – Print is easier to read than cursive4. Minimize abbreviations – Avoid abbreviations, but when needed use

a consistent rule such as 3 – 4 letter truncation.• Example: NAVAIRWARCENTRASYSDIV

5. Space between words or strings – separating strings into chunks makes it easier to read and remember• Example: (850) 555-1234

Feature Analysis Feature Analysis Object PerceptionObject Perception

Geons (Biederman) – fundamental geometric shapes that are combined to produce all other complex objects

We recognize an object by:1. Breaking object into geons2. Categorizing each geon on basis of feature match3. 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 ProcessingTop-down & Bottom-up Processing

Bottom-up processing (data-driven) – object recognition guided by sensory featuresTop-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 ProcessingTop-down & Bottom-up Processing Guidelines for text and icon designGuidelines for text and icon design

1. Optimize bottom-up processing• Ease of viewing and discrimination - size, contrast.

2. Optimize top-down processing• Use actual words, not random text strings• Minimize number of words that need to be recognized• Provide context information

3. Evaluate tradeoffs• Given limited space weigh importance of optimal

viewing conditions vs. availability of context4. Usability testing

• When testing for usability DO include context in which stimulus will actually be seen

Working MemoryWorking Memory

Centralexecutive

Visuospatialsketchpad

Phonologicalloop

Working MemoryWorking 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 ExecutiveCentral Executive – attentional control system that coordinates info from other two subsystems.• Visuospatial SketchpadVisuospatial Sketchpad – holds info in an analog spatial form while it is being used.

• Mental imagery• Phonological LoopPhonological Loop – represents verbal information in an acoustical form while it is being rehearsed.

• Sub-vocal articulation

Baddeley’s model of working memory

Spatial AbilitySpatial Ability

a. b. c. d.

Which two of the four shapes below are the same as this one?

*Vandenberg & Kuse

As you try to answer this question, how is the central executive allocating your attentional resources?

Human Factors Implications of Human Factors Implications of Working Memory LimitsWorking Memory Limits1. Minimize working memory load

• Keep the memory requirement short and small enough for WM

2. Provide visual echoes• Hard copy is not subject to decay

3. 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

4. Minimize confusability• Create visual, audio, or spatial distinctions

5. Exploit different working-memory codes• Verbal info interferes more with other verbal info than with spatial

info

6. Ordering of text and instructions• Order instructions congruently with order in which task accomplished

Long-Term MemoryLong-Term Memory

Long-Term MemoryLong-Term Memory – Nearly permanent storage of information with unlimited capacity

EncodingEncoding – placing info into memory

StorageStorage – keeping info in memory

RetrievalRetrieval – accessing information from LTM back into WM

ForgettingForgetting

ForgettingForgetting – caused by decay, interference, or inability to access (retrieve) information.

Memory retrieval fails due to:1. Weak item strength due to low frequency or recency of

reactivation• Ex: Password that is accessed once a semester

2. Weak or few associations of item with other info• Ex: (apple – red – fire – water)

3. Interfering associations• Ex: giving your current spouse an anniversary card on

the anniversary of your previous marriage.

Organization of info in LTMOrganization of info in LTM

• Semantic NetworksSemantic 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?

• SchemaSchema – One’s entire knowledge structure about a given topic• Experts knowledge may be structured very differently from novices

• Mental ModelsMental Models – They way in which one expects a system to work.

• Population StereotypePopulation Stereotype – similar mental models held by many people.• ex: light switch is on in up position, hot water knob is on the left

Which question is answered more readily:A: Are canaries yellow?B: Do canaries have skin?

LTM implications for designLTM 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

“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!”

• Example: After recognizing the difficulty South Florida voters were having with their ballots, the following instructions were issued:

LTM implications for designLTM implications for designDesign SolutionsDesign Solutions1. Encourage regular use of information

• this will improve frequency and recency for ease of recall2. Standardize

• Lessens amount of learning required when using new system• Ex: where is the wiper function control located in your car?

3. Use memory aids• Software menus provide info visible in sensory store, whereas

command code must be retrieved from LTM4. 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

5. Encourage active verbalization6. Design info to be consistent with user stereotypes7. Design to support development of mental models

• Input options and system state should be clearly visible

Declarative KnowledgeDeclarative Knowledge – (What) concepts, facts, principles, rules, mental models

- gained quickly, decays rapidly- ex: rules of the road

Procedural KnowledgeProcedural Knowledge – (How) implicit knowledge of how to perform a skill

- takes longer to acquire, fades slowly- ex: driving

Declarative & Procedural Declarative & Procedural KnowledgeKnowledge

NOVICE

EXPERT

Episodic MemoryEpisodic 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 MemoryProspective 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

Event Memory: Event Memory: Episodic & ProspectiveEpisodic & Prospective

To Do:To Do:

AttentionAttention

Selective AttentionSelective Attention – allows us to process important information - ex: “cocktail party effect”

Focused AttentionFocused Attention – allows us to filter out unwanted information- ex: studying with the radio on

Divided AttentionDivided Attention – allows us to perform multiple tasks at once- ex: driving while tuning the stereoTime-SharingTime-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?

Due to limited attentional resources, humans must allocate attention appropriately

Automatic vs. Controlled Automatic vs. Controlled ProcessingProcessing

Blue Blue Red Red Green Green YellowYellow

Green Green Red Red Yellow Yellow BlueBlue

Red Red YellowYellow Green Green BlueBlue

YellowYellow Green Green BlueBlue RedRed

GreenGreen BlueBlue RedRed YellowYellowStroop Effect

Controlled ProcessingControlled Processing – effortful cognitive processes requiring attention to initiate and sustain (processing unfamiliar info)Automatic ProcessingAutomatic Processing – processing performed with little demand on attention (well practiced tasks)

Attentional Resources Attentional Resources AllocationAllocationEasiest to time-share limited resources when the two tasks:1. Differ in terms of whether the info is processed early (e.g., perception)

and late (e.g., response selection) stages2. Require different input modalities (visual vs auditory)3. Differ in terms of input to response coding (verbal/vocal vs

visual/manual)

PerceivingPerceiving Central ProcessingCentral Processing ResponseResponse

PrintPrint SpeechSpeech

Logical problem solvingLogical problem solvingRehearsal: digits/wordsRehearsal: digits/words Mental arithmeticMental arithmetic

VoiceVoice

Analog quantitiesAnalog quantities Flow fieldFlow field Spatial patternsSpatial patterns

Mental rotationMental rotation

ImagingImaging

Manually Manually guided responseguided response

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