CognitionCognition

Chapter 6Chapter 6

CognitionCognition The basic mechanism by which The basic mechanism by which

people perceive, think, and people perceive, think, and rememberremember

Three stagesThree stages1.1. Perceptual stage – bring in information Perceptual stage – bring in information

and compare it to memoryand compare it to memory

2.2. Cognitive stage – central processing or Cognitive stage – central processing or thought stagethought stage

3.3. Action stage – brain selects a responseAction stage – brain selects a response

Object and Pattern Object and Pattern PerceptionPerception

Feature Analysis – to give meaning to stimuli, Feature Analysis – to give meaning to stimuli, features are analyzed individually and compared to features are analyzed individually and compared to features and patterns stored in long-term memoryfeatures and patterns stored in long-term memory

Text perception – letter features are familiar and Text perception – letter features are familiar and analyzed quickly without our awareness. analyzed quickly without our awareness. Perception is hierarchical manner. Features are Perception is hierarchical manner. Features are combined into letters, letters into words, and words combined into letters, letters into words, and words into sentences.into sentences.– Features compatible with stored memoryFeatures compatible with stored memory– Upper-& lowercase – Capital letters for individual Upper-& lowercase – Capital letters for individual

words and mix in sentence structurewords and mix in sentence structure– Use Print for Test DisplayUse Print for Test Display– Minimize AbreviationsMinimize Abreviations– Gaps between words or character strings are Gaps between words or character strings are

importantimportant

Object and Pattern Object and Pattern Perception (cont.)Perception (cont.) In recognizing shape of object, only edges of In recognizing shape of object, only edges of

geons are important. Not so when geons are important. Not so when discriminating between two similar objects discriminating between two similar objects such as an orange and a basket ball.such as an orange and a basket ball.

Top-Down & Bottom-Up Top-Down & Bottom-Up Processing(Context)Processing(Context)

Top-down & bottom-up occurs Top-down & bottom-up occurs simultaneously with text, drawings, icons, simultaneously with text, drawings, icons, photos, and auditory stimuliphotos, and auditory stimuli

Redundancy principle – when we read an Redundancy principle – when we read an incomplete word or sentence, we can figure incomplete word or sentence, we can figure it out because of redundancy in top-down it out because of redundancy in top-down processingprocessing

Top-Down & Bottom-Up Top-Down & Bottom-Up Processing (trade-offs)Processing (trade-offs)

High quality stimulus uses bottom-up. As High quality stimulus uses bottom-up. As quality degrades, top-down takes over using quality degrades, top-down takes over using context and redundancycontext and redundancy

Design GuidelinesDesign Guidelines Optimize bottom-up processing – critical Optimize bottom-up processing – critical

factors: size, contrast, etc.factors: size, contrast, etc.– Optimize top-down processing – use more Optimize top-down processing – use more

words, but restrict vocabularywords, but restrict vocabulary– Evaluate trade-offsEvaluate trade-offs– Test usability with users in environment Test usability with users in environment

intended for useintended for use Icons – must be both recognized and interpretedIcons – must be both recognized and interpreted

Transfer to Working Transfer to Working MemoryMemory Information, once recognized, either leads Information, once recognized, either leads

directly to a response or moves to working directly to a response or moves to working memory for further processing.memory for further processing.

Working Memory is the temporary work bench of Working Memory is the temporary work bench of the mind where information is transformed and the mind where information is transformed and acted on. acted on.

The sensory registry holds visual information The sensory registry holds visual information about 1 sec and audio about 3-5 sec. During about 1 sec and audio about 3-5 sec. During that time attention may be focused on a subset that time attention may be focused on a subset & brought into working memory for further & brought into working memory for further processingprocessing

This attention process is called “selective This attention process is called “selective attention”. Is analogous to a spotlight.attention”. Is analogous to a spotlight.

Working MemoryWorking Memory Working memory (short-term memory) – prone Working memory (short-term memory) – prone

to frequent failure. Most failures are to frequent failure. Most failures are inconsequential, but sometimes catastrophicinconsequential, but sometimes catastrophic

Long-term Memory – storage of information Long-term Memory – storage of information after it is no longer active.after it is no longer active.

While we are performing central information While we are performing central information processing, we bring information from the processing, we bring information from the sensory register and long term memory into sensory register and long term memory into working memory.working memory.

Working Memory Working Memory LimitationsLimitations Capacity – About 7 +/- 2 chunks of information. A Capacity – About 7 +/- 2 chunks of information. A

chunk is the unit of working memory work space chunk is the unit of working memory work space defined jointly by the physical and cognitive defined jointly by the physical and cognitive properties that bind information together.properties that bind information together.

Time – strength in working memory can be increased Time – strength in working memory can be increased by rehearsing (repeating a 7 digit tele# number by rehearsing (repeating a 7 digit tele# number several times before dialing). The half-life of several times before dialing). The half-life of working memory is ab0ut 7 seconds for a memory working memory is ab0ut 7 seconds for a memory store of 3 chunks & 70 seconds for 1 chunk.store of 3 chunks & 70 seconds for 1 chunk.

Human Factors Human Factors Implications of Working Implications of Working Memory LimitationsMemory Limitations1.1. Minimize working memory loadMinimize working memory load2.2. Provide visual echoesProvide visual echoes3.3. Exploit chunkingExploit chunking

– Physical chunk size – optimal is 3 - 4 numbers or letters Physical chunk size – optimal is 3 - 4 numbers or letters per chunk.per chunk.

– Meaningful sequences – e.g., 555, JUNE, 4321, etc.Meaningful sequences – e.g., 555, JUNE, 4321, etc.– Superiority of letters over numbers because of greater Superiority of letters over numbers because of greater

potential for meaningfulness. potential for meaningfulness. – Keeping numbers separate from letters (GST 458 is better Keeping numbers separate from letters (GST 458 is better

than GST458)than GST458)4.4. Minimize confusabilityMinimize confusability5.5. Exploit different working memory codes – visual & verbalExploit different working memory codes – visual & verbal6.6. Ordering of text & instructions – good and logical grammar. Ordering of text & instructions – good and logical grammar.

Long-Term MemoryLong-Term Memory Learning is the processing and Learning is the processing and

storing information in long-term storing information in long-term memorymemory– Semantic memory - general knowledgeSemantic memory - general knowledge– Event memory - specific events Event memory - specific events – Episodic memory - significant event of Episodic memory - significant event of

past past – Prospective memory - remembering to Prospective memory - remembering to

do something in futuredo something in future

Basic MechanismsBasic MechanismsTasks require us to think about task-relevant Tasks require us to think about task-relevant

information – interpret displays, choose responses, information – interpret displays, choose responses, etc. Activates material in working memory which etc. Activates material in working memory which may be triggered by perception or may be triggered may be triggered by perception or may be triggered directly by long-term memory (recalling to-do item).directly by long-term memory (recalling to-do item).

Item Strength – depends on frequency and recency Item Strength – depends on frequency and recency of activation.of activation.

Associations – associating different items from long- Associations – associating different items from long- term memory and using in working memory (setting term memory and using in working memory (setting up a machine or what you ate for breakfast up a machine or what you ate for breakfast yesterday).yesterday).

Forgetting – decay of item strength and association Forgetting – decay of item strength and association strength occurs at an exponential rate.strength occurs at an exponential rate.

Organization of Organization of Information in Long-Term Information in Long-Term MemoryMemory Stored in a network of associationsStored in a network of associations Much of knowledge used daily is stored in semantic Much of knowledge used daily is stored in semantic

networks –network sections are then dedicated to networks –network sections are then dedicated to event, episodic, & prospective memories.event, episodic, & prospective memories.

Parallel processing – we often reactivate a memory Parallel processing – we often reactivate a memory by simultaneously thinking of several semantically by simultaneously thinking of several semantically related concepts which spreads to associated related concepts which spreads to associated concepts.concepts.

Schemas – long-term memory tends to be Schemas – long-term memory tends to be organized around central concepts or topics are organized around central concepts or topics are called schemas.called schemas.

Mental Models – schemas of dynamic systems are Mental Models – schemas of dynamic systems are called mental models (e.g., all cell phones work called mental models (e.g., all cell phones work similarly so user works on basis of expectancies)similarly so user works on basis of expectancies)

Implications for DesignImplications for Design Encourage regular use of information to increase Encourage regular use of information to increase

frequency and recency.frequency and recency. Standardize - uses mental models.Standardize - uses mental models. Use memory aids – for infrequent tasks provide Use memory aids – for infrequent tasks provide

procedure lists, help, etc.procedure lists, help, etc. Carefully design information to be rememberedCarefully design information to be remembered

– Meaningful to user (semantically associated with Meaningful to user (semantically associated with other info)other info)

– Concrete rather than abstract wordsConcrete rather than abstract words– Distinctive concepts not confused with othersDistinctive concepts not confused with others– Sets of info organized into associated groupsSets of info organized into associated groups– Item should be able to be guessed based on Item should be able to be guessed based on

other assoc. info.other assoc. info.– Adequate context & background knowledge Adequate context & background knowledge

without tech jargonwithout tech jargon

Implications for Design Implications for Design (cont.)(cont.)

Encourage active verbalization or Encourage active verbalization or production of information that is to be production of information that is to be recalled – taking notes in class, restating recalled – taking notes in class, restating what you heard in your own words, etc.what you heard in your own words, etc.

Design information toe be consistent with Design information toe be consistent with existing mental models – DVD players, existing mental models – DVD players, cameras, cell phones, etc.cameras, cell phones, etc.

Design to support development of mental Design to support development of mental models – this was done with symbols and models – this was done with symbols and icons on the above mentioned itemsicons on the above mentioned items

Declarative & Procedural Declarative & Procedural KnowledgeKnowledge Declarative Knowledge – knowledge about Declarative Knowledge – knowledge about

things that we can verbalize and is retrieved things that we can verbalize and is retrieved from semantic networks.from semantic networks.

Procedural Knowledge – not part of previous Procedural Knowledge – not part of previous discussions and is implicit and skills based but discussions and is implicit and skills based but not easily verbalized (e.g., we can learn a not easily verbalized (e.g., we can learn a language, but find it hard to describe how we language, but find it hard to describe how we do it or learn how to ride a bike, but cannot do it or learn how to ride a bike, but cannot describe exactly how we developed this skill). describe exactly how we developed this skill).

Both are learned simultaneously – declarative Both are learned simultaneously – declarative is easier to learn but decays quickly and is easier to learn but decays quickly and procedural is harder to learn but decays procedural is harder to learn but decays slowly.slowly.

Attention & Mental Attention & Mental ResourcesResources

Mental processing requires use of mental Mental processing requires use of mental resources. In multitasking environments, focus on resources. In multitasking environments, focus on one task is always at the expense of the others one task is always at the expense of the others due to limited resources.due to limited resources.

Attention & Time-Sharing – Attention & Time-Sharing – selective attention selective attention allows us to process important info and allows us to process important info and focused focused attention attention allows us to filter out unwanted. When allows us to filter out unwanted. When both are needed simultaneously, we time-share both are needed simultaneously, we time-share e.g., driving a car. Deteriorates as we get older.e.g., driving a car. Deteriorates as we get older.– Design tasks to minimize time sharingDesign tasks to minimize time sharing– Measure/predict attention required by each Measure/predict attention required by each

tasktask– Measure/predict a person’s ability to perform Measure/predict a person’s ability to perform

multiple tasksmultiple tasks

Automaticity: Controlled Automaticity: Controlled vs Automatic Processingvs Automatic Processing

Controlled Processing – cognitive processes that Controlled Processing – cognitive processes that require attention to initiate & sustainrequire attention to initiate & sustain

Automatic Processing – cognitive processes become Automatic Processing – cognitive processes become automatic through repeated usage and consistent automatic through repeated usage and consistent mapping.mapping.

For example, skilled piano player sight reading music For example, skilled piano player sight reading music (automatic) and carrying on conversation (controlled) (automatic) and carrying on conversation (controlled) at the same time or driver attending to driving tasks at the same time or driver attending to driving tasks (automatic) while talking to passenger (controlled).(automatic) while talking to passenger (controlled).

Practice of consistent tasks produces automaticity and Practice of consistent tasks produces automaticity and time-sharing skillstime-sharing skills

Time-sharing efficiency increases when multiple tasks Time-sharing efficiency increases when multiple tasks have similar physical and cognitive structures.have similar physical and cognitive structures.

Multiple Resource Multiple Resource DichotomiesDichotomies

1.1. Stages: early vs late processing – perceptual & Stages: early vs late processing – perceptual & central processing (early) are largely separated central processing (early) are largely separated from response processing (late). Responding will from response processing (late). Responding will not significantly interfere with perception, but not significantly interfere with perception, but adding another response activity does interfere.adding another response activity does interfere.

2.2. Input Modalities: visual vs auditory – better at Input Modalities: visual vs auditory – better at dividing attention between 1 visual & 1 auditory dividing attention between 1 visual & 1 auditory than between 2 visual or 2 auditorythan between 2 visual or 2 auditory

3.3. Processing Codes: spatial vs verbal in early Processing Codes: spatial vs verbal in early processing and manual vs vocal responding – processing and manual vs vocal responding – depend on distinct resources. Time-sharing depend on distinct resources. Time-sharing efficiency increases to the extent that any two efficiency increases to the extent that any two tasks draw on separate resources (e.g., piano tasks draw on separate resources (e.g., piano player, voice dialing of cell phone while driving. player, voice dialing of cell phone while driving. Confusion is likely to increase by similarity of Confusion is likely to increase by similarity of information processed.information processed.

General Implications General Implications for Designfor Design Input modes, response devices, and tasks Input modes, response devices, and tasks

should be combined so that they are should be combined so that they are dissimilar as possible regarding processing dissimilar as possible regarding processing stages, input modalities, and processing stages, input modalities, and processing codes.codes.

Greater automation of a task the better the Greater automation of a task the better the time-sharing capabilitytime-sharing capability

Information should be provided so that the Information should be provided so that the person knows the importance of each task person knows the importance of each task and therefore how to allocate resources and therefore how to allocate resources between tasks.between tasks.