Description
Interaction is a kind of action that occurs as two or more objects have an effect upon one another. The idea of a two-way effect is essential in the concept of interaction, as opposed to a one-way causal effect.
Human factors in n interaction design
Projects
• Project Phase One reports are due in three weeks: March 26. • Submit a printed hard-copy of your report in class on March 26. • You are going to have two months after Phase One to finish your project and present it in class. class • Check the newsgroup for possible announcements related l d to the h project.
Projects
• What do I want to see in Phase One reports apart from a general description?
– Description of your potential users
• Age, gender, physical and cognitive abilities, education, cultural or ethnic background, training, motivation, ti ti goals l and d personality lit • Skill level of your users: Novice or first-time users, Knowledgeable g users, , or expert p frequent q users
– Identification of the tasks
• • • • Users’ needs? Observing and interviewing users Decomposition of high level tasks R l ti Relative task t kf frequencies i
Projects
– What type of interaction style will be employed?
• • • • • • Direct manipulation? Menu selection? F Form fill-in? fill i ? Command language? Natural language, language speech? Vision?
– Which tools ( (software/hardware) / ) are y you planning to use in your project?
Many kinds of interaction styles available…
• • • • • • • • • • Command Speech Data-entry Data entry Form fill-in Query Graphical Web Pen Augmented reality Gesture and even...
for Human–Computer Human Computer Interaction
understand your materials • understand computers
– limitations, limitations capacities capacities, tools tools, platforms
• understand people
– psychological, social aspects – human error
• and their interaction …
Usability measures
• 5 human factors central to interface evaluation:
– Time to learn • How long does it take for typical members of the community to learn relevant task? – Speed of performance • How long does it take to perform relevant benchmarks? – Rate of errors by users • How many and what kinds of errors are made during benchmark tasks? – Retention over time • Frequency F of f use and d ease of f learning l i – Subjective satisfaction • Allow for user feedback via interviews, , free-form comments and satisfaction scales
Designing for people:
•Example airplane errors:
–If booster pump fails, turn on fuel valve within 3 seconds –Tests showed it took at least five seconds to actually ll d do i it! !
•Result
–Human factors became critically important
Differences Between The Designer g And Operator
Darn these hooves! I h hit t the wrong sw switch tch again! aga n! Who designs these instrument panels, raccoons?
The human
• Information i/o …
– visual, auditory, haptic, movement
• Information stored in memory
– se sensory, so y, short-term, s o t te , long-term o g te
• Information processed and applied
– reasoning, reasoning problem solving, solving skill, skill error
• Emotion influences human capabilities • Each E h person is i different diff t
Core cognitive aspects
• Attention • Perception and recognition • Memory • Reading, g, speaking p g and listening g • Problem-solving, planning, reasoning and decision-making decision making, learning
Vision
Two stages in vision • physical reception of stimulus • processing and interpretation of stimulus
The Eye - physical reception
• mechanism for f receiving light and transforming it into electrical energy • light l h reflects fl f from objects b • images are focused upside-down on retina • retina contains rods for low light vision and d cones f for color l vision i i • ganglion cells (brain!) detect pattern and d movement
Interpreting the signal
• Size and depth
– visual angle indicates how much of view object b occupies
(relates to size and distance from eye)
– visual i l acuity it i is the th ability bilit t to perceive i d detail t il
(limited)
– familiar objects perceived as constant size
(in spite of changes in visual angle when far away)
– cues like overlapping pp g help pp perception p of size and depth
Interpreting the signal (cont)
• Brightness h
– – – – subjective reaction to levels of light affected by luminance of object measured by just noticeable difference visual acuity increases with luminance as does flicker made up of hue, intensity, saturation cones sensitive to color wavelengths blue acuity is lowest 8% males and 1% females color blind
• Color
– – – –
color and 3D
• both often used very badly! • color
– – – – older monitors limited palette color over used because ‘it is there’ beware color blind! use sparingly to reinforce other information
• 3D effects
– good for physical information and some graphs – but if over used … e.g. text in perspective!! 3D pie charts
bad use of color
• over use site) without very good reason (e.g. kids’
• colour blindness • poor use of contrast • do adjust your set!
– adjust your monitor to greys only – can you still read your screen?
Interpreting the signal (cont)
• The visual system compensates for:
– movement – changes in luminance.
• Context is used to resolve ambiguity • Optical illusions sometimes occur due to over compensation
Optical Illusions
the Ponzo illusion
the Muller Lyer illusion
Reading
• Several l stages:
– visual pattern perceived – decoded using internal representation of language – interpreted using knowledge of syntax, semantics, pragmatics
• • • •
Reading involves saccades and fixations Perception occurs during fixations Word shape is important to recognition Negative g contrast improves p reading g from computer screen
Hearing
• Provides d information f about b environment:
distances, directions, objects etc.
• Physical apparatus:
– outer ear – protects inner and amplifies sound – middle ear – transmits sound waves as – inner ear
vibrations to inner ear – chemical transmitters are released and cause impulses in auditory nerve
• Sound
– pitch – loudness – timbre – sound frequency – amplitude – type or quality
Hearing (cont)
• Humans can hear frequencies from 20Hz to 15kHz
– l less accurate t distinguishing di ti i hi high hi h f frequencies i th than low.
• Auditory system filters sounds
– can attend to sounds over background g noise.
Touch
• Provides important feedback about environment. • May be key sense for someone who is visually impaired. • Stimulus received via receptors in the skin:
– thermoreceptors – nociceptors – mechanoreceptors – heat and cold – pain – pressure
(some instant, some continuous)
• Some areas more sensitive than others e.g. fingers. • Kinethesis - awareness of body position
– affects comfort and performance.
Movement
• Time taken k to respond d to stimulus: l reaction time + movement time • Movement time dependent on age, fitness etc. • Reaction time - dependent on stimulus type:
– visual ~ 200ms – auditory ~ 150 ms – pain ~ 700ms
Movement (cont)
• Fitts' ' Law describes d b the h time taken k to hit h a screen target: Mt = a + b log2(D/S + 1)
where: a and b are empirically p y determined constants Mt is movement time D is Distance S is Si Size e of target ta get
? targets as large as possible distances as small as possible
Att ti Attention
• Selecting things to concentrate on from the mass around us, at a point in time • F Focussed d and d divided di id d attention tt ti enables bl us to t b be selective in terms of the mass of competing stimuli but limits our ability to keep track of all events
– magicians use this h to their h advantage! d
• Information at the interface should be structured to capture users users’ attention attention, e e.g. g use perceptual boundaries (windows), color, reverse video, sound and flashing lights
Design implications for attention
• Make information salient when it needs attending to • Use techniques that make things stand out like color, ordering, d i spacing, i underlining, d li i sequencing i and d animation • Avoid cluttering the interface - follow the google.com google com example of crisp, simple design • Avoid using too much because the software allows it
An example of over-use of graphics
Our Situation
? State St t
the th bad b d news ? Be clear, don’t try to obscure the situation
Perception and recognition
• How information is acquired from the world and transformed into experiences • Obvious implication is to design representations that are readily perceivable, g e.g.
– Text should be legible – Icons should be easy to distinguish and read
Which is easiest to read and why?
What is the time?
What is the time?
What is the time?
What is the time?
What is the time?
Memory
There are three types of memory function: Sensory memories Sh t t Short-term memory or working ki memory
Long-term memory
Memory
• I Involves l encoding di and d recalling lli k knowledge l d and d acting ti appropriately don t remember everything - involves filtering and • We don’t processing • Context is important in affecting our memory • We recognize things much better than being able to recall things
– The rise of the GUI over command-based interfaces
• Better at remembering images than words
– The use of icons rather than names
sensory memory
• Buffers for stimuli received through senses
– iconic memory: visual stimuli – echoic memory: aural stimuli – haptic memory: tactile stimuli
• Example a pe
– stereo sound
• Continuously overwritten
Short term memory (STM) Short-term
• Scratch-pad for temporary recall
– rapid id access ~ 70ms 70 – rapid decay ~ 200ms – limited capacity p y - 7± 2 chunks
Examples
212348278493202 0121 414 2626 HEC ATR ANU PTH ETR EET
The problem with the classic ‘7 7±2 2’
• George Miller’s Miller s theory of how much information people can remember • People People’s s immediate memory capacity is very limited • Many designers have been led to believe that this is useful finding g for interaction design g
Wh t some designers What d i get t up to… t
• • • • • Present only 7 options on a menu Display only 7 icons on a tool bar Have no more than 7 bullets in a list Place only 7 items on a pull down menu Place only 7 tabs on the top of a website page
– But this is wrong? Why?
Wh ? Why?
• Inappropriate I i t application li ti of f th the th theory • People can scan lists of bullets, tabs, menu items till they see the one they want • They don’t have to recall them from memory having only briefly heard or seen them • Sometimes a small number of items is good design • But it depends on task and available screen estate
Long term memory (LTM) Long-term
• Repository for all our knowledge
– slow access ~ 1/10 second – slow l d decay, if any – huge or unlimited capacity
• Two types
– episodic – serial memory of events – semantic – structured memory of facts,concepts, skills semantic LTM derived from episodic LTM
Long term memory (cont.) Long-term (cont )
• Semantic memory structure
– provides access to information – represents t relationships l ti hi b between t bit bits of f information i f ti – supports inference
• Model: semantic network
– inheritance – child nodes inherit properties of parent nodes d – relationships between bits of information explicit – supports inference through inheritance
LTM - semantic network
Models of LTM - Frames
• Information organized in data structures • Slots in structure instantiated with values for instance of data • Type–subtype relationships
DOG
Fixed Fi d legs: 4 Default diet: carniverous sound: bark Variable size: color l
COLLIE
Fixed Fi d breed of: DOG type: sheepdog Default size: 65 cm Variable color
Models of LTM - Scripts
Model of stereotypical information required to interpret situation Script has elements that can be instantiated with values for context
Script for a visit to the vet
Entry conditions: dog ill vet open owner has money Result: dog better owner poorer vet richer examination table medicine instruments Scenes: Roles: vet examines diagnoses treats owner brings dog in pays takes dog out arriving at reception waiting in room examination paying dog needs medicine dog needs operation
Props:
Tracks:
Models of LTM - Production rules
Representation of procedural knowledge. C d Condition/action / rules l
if condition is matched then use rule to determine action.
IF dog is wagging tail THEN pat dog IF dog is growling THEN run away
LTM - Storage of information
• rehearsal
– information moves from STM to LTM
• total time hypothesis
– amount retained proportional to rehearsal time
• distribution of practice effect
– optimized p by y spreading p g learning g over time
• structure, meaning and familiarity
– information easier to remember
LTM - Forgetting
decay
– information is lost gradually but very slowly
interference
– new information replaces old: retroactive interference – old may interfere with new: proactive inhibition so may not forget at all memory is selective … … affected by emotion – can subconsciously `choose' to forget
LTM - retrieval
recall
– information reproduced from memory can be assisted i t db by cues, e.g. categories, t i imagery i
recognition
– information gives knowledge that it has been seen before – less complex than recall - information is cue
Thinking
Reasoning
deduction, induction, abduction
Problem solving
Deductive Reasoning
• Deduction: d
– derive logically necessary conclusion from given premises. p e.g. If it is Friday then she will go to work It is Friday Therefore she will go to work. work
Deduction (cont.) (cont )
• When truth and logical validity clash …
e.g. Some people are babies Some babies cry Inference - Some people cry
Correct?
Inductive Reasoning
• Induction: d
– generalize from cases seen to cases unseen e g all elephants we have seen have trunks e.g. therefore all elephants have trunks.
• Unreliable:
– can only prove false not true
… but useful! • Humans not good at using negative evidence
– e.g. Wason’s cards
Wason's Wason s cards
7 E 4 K
If a card has a vowel on one side it has an even number on the other Is this true? How many cards do you need to turn over to find out? …. and which cards?
Abductive reasoning
• reasoning from event to cause
e.g. Sam drives fast when drunk. If I see Sam driving fast, assume drunk.
• Unreliable:
– can lead to false explanations p
Problem solving
• Process of f finding f d solution l to unfamiliar f l task k using knowledge. • Several theories. • Gestalt
– problem solving both productive and reproductive – productive draws on insight and restructuring of problem – attractive but not enough evidence to explain `insight' insight' etc. – move away from behaviourism and led towards information processing theories
Problem solving (cont.) (cont )
Problem space theory
– problem space comprises problem states – problem bl solving l i i involves l generating ti states t t using i l legal l operators – heuristics may y be employed p y to select operators p e.g. means-ends analysis – operates within human information processing system e g STM limits etc. e.g. etc – largely applied to problem solving in well-defined areas e.g. puzzles rather than knowledge intensive areas
Problem solving (cont.) (cont )
• Analogy l
– analogical mapping:
• novel p problems in new domain? • use knowledge of similar problem from similar domain
– analogical mapping difficult if domains are semantically different
• Skill acquisition
– skilled activity characterized by chunking
• lot of information is chunked to optimize STM
– conceptual rather than superficial grouping of problems – information is structured more effectively
Errors and mental models
Types of f error • slips p
– right intention, but failed to do it right – causes: poor physical skill,inattention etc. – change to aspect of skilled behaviour can cause slip
• mistakes
– wrong intention – cause: incorrect understanding
humans create mental models to explain p behaviour. if wrong (different from actual system) errors can occur
Mental models
• Users develop an understanding of a system through learning & using it • Knowledge is often described as a mental model
– How to use the system (what to do next) – What to do with unfamiliar systems or unexpected situations (how the system works)
• P People l make k inferences i f using i mental l models d l of f how to carry out tasks
M t l models Mental d ls
• Craik (1943) described mental models as internal constructions of some aspect of the external world enabling predictions to be made • Involves unconscious and conscious processes, where images and analogies are activated • Deep versus shallow models (e.g. how to ) drive a car and how it works)
Everyday reasoning & mental models
(a) You arrive home on a cold winter’s night to a cold house. How do you get the house to warm up as quickly as possible? poss b e Set Se the e thermostat e os a to o be at a its s highest g es or o to o the e desired temperature? (b) You arrive home starving hungry hungry. You look in the fridge and find all that is left is an uncooked pizza. You have an electric oven. Do you warm it up to 375 degrees first and then put it in (as specified by the instructions) or turn the oven up higher to try to warm it up quicker?
Heating g up p a room or oven that is thermostat-controlled
• Many people have erroneous mental models (Kempton, 1996) • Why?
– General valve theory, where ‘more is more’ principle i generalised is li d to t different diff t settings tti (e.g. ( gas pedal, d l gas cooker, tap, radio volume) – Thermostats based on model of on-off switch model
Heating g up p a room or oven that is thermostat-controlled
• Same is often true for understanding how interactive devices and computers work:
– P Poor, often ft incomplete, i l t easily il confusable, f bl based b d on inappropriate analogies and superstition (Norman, 1983) – e.g. frozen cursor/screen - most people will bash all manner of keys
External cognition
• Concerned with explaining how we interact with external representations (e.g. maps, notes, , diagrams) g ) • What are the cognitive benefits and what processes involved • How they extend our cognition • What computer-based representations can we develop to help even more?
Externalizing g to reduce memory y load
• Diaries, reminders,calendars, notes, shopping lists, to-do lists - written to remind us of what to do • Post-its, piles, marked emails - where placed indicates priority of what to do • External representations:
– Remind us that we need to do something (e.g. to buy something g for mother’s day) y) – Remind us of what to do (e.g. buy a card) – Remind us when to do something (e.g. send a card by a certain date) )
Computational offloading
• When a tool is used in conjunction with an external representation to carry out a computation (e.g. pen and paper) ) • Try doing the two sums below (a) in your head, (b) on a piece of paper and c) with a calculator.
– 234 x 456 =?? – CCXXXIIII x CCCCXXXXXVI = ???
• Which is easiest and why? Both are identical sums
Annotation i and d cognitive i i tracing i
• Annotation involves modifying existing representations through making marks
– e.g. crossing i off, ff ticking, ti ki underlining d li i
• Cognitive tracing involves externally manipulating items into different orders or structures
– e.g. playing scrabble, playing cards
Emotion
• Various theories of how emotion works
– James-Lange: g emotion is our interpretation p of a physiological response to a stimuli – Cannon: emotion is a psychological response to a stimuli – Schacter-Singer: emotion is the result of our evaluation of our physiological responses, in the light of the whole situation we are in
• Emotion clearly involves both cognitive and physical responses to stimuli
Emotion (cont.) (cont )
• The biological response to physical stimuli is called affect • Affect influences how we respond p to situations
– positive ? creative problem solving – negative ? narrow thinking
“Negative affect can make it harder to do even easy tasks; positive affect can make it easier to do difficult tasks”
(Donald Norman)
Emotion (cont.) (cont )
• Implications for interface design
– stress will increase the difficulty of problem solving – relaxed users will be more forgiving of shortcomings h i i in d design i – aesthetically pleasing and rewarding interfaces will increase positive affect
Individual differences
• long term – gender, physical and intellectual abilities • short h t term t – effect of stress or fatigue • changing – age Ask yourself: will design decision exclude section of user population? l ti ?
Psychology y gy and the Design g of Interactive System
• Some S direct di applications li i
– e.g. blue acuity is poor ? blue should not be used for important detail
• However, correct application generally requires g of context in p psychology, y gy, and an understanding understanding of particular experimental conditions
Involving users in the design
• At the very least, talk to users
– It It’s s surprising how many designers don’t!
• Contextual Inquiries
– Interview users in their usage place l ( (e.g., office), ff ) during d i their h i normal routine (e.g., while working) k ) – Used to discover user’s culture, requirements, expectations, etc.
Involving users in the design
• Create prototypes
– It It’s s hard to comment on something that doesn’t yet exist – Users are good at giving feedback for something that is even partially built
doc_893231804.pdf
Interaction is a kind of action that occurs as two or more objects have an effect upon one another. The idea of a two-way effect is essential in the concept of interaction, as opposed to a one-way causal effect.
Human factors in n interaction design
Projects
• Project Phase One reports are due in three weeks: March 26. • Submit a printed hard-copy of your report in class on March 26. • You are going to have two months after Phase One to finish your project and present it in class. class • Check the newsgroup for possible announcements related l d to the h project.
Projects
• What do I want to see in Phase One reports apart from a general description?
– Description of your potential users
• Age, gender, physical and cognitive abilities, education, cultural or ethnic background, training, motivation, ti ti goals l and d personality lit • Skill level of your users: Novice or first-time users, Knowledgeable g users, , or expert p frequent q users
– Identification of the tasks
• • • • Users’ needs? Observing and interviewing users Decomposition of high level tasks R l ti Relative task t kf frequencies i
Projects
– What type of interaction style will be employed?
• • • • • • Direct manipulation? Menu selection? F Form fill-in? fill i ? Command language? Natural language, language speech? Vision?
– Which tools ( (software/hardware) / ) are y you planning to use in your project?
Many kinds of interaction styles available…
• • • • • • • • • • Command Speech Data-entry Data entry Form fill-in Query Graphical Web Pen Augmented reality Gesture and even...
for Human–Computer Human Computer Interaction
understand your materials • understand computers
– limitations, limitations capacities capacities, tools tools, platforms
• understand people
– psychological, social aspects – human error
• and their interaction …
Usability measures
• 5 human factors central to interface evaluation:
– Time to learn • How long does it take for typical members of the community to learn relevant task? – Speed of performance • How long does it take to perform relevant benchmarks? – Rate of errors by users • How many and what kinds of errors are made during benchmark tasks? – Retention over time • Frequency F of f use and d ease of f learning l i – Subjective satisfaction • Allow for user feedback via interviews, , free-form comments and satisfaction scales
Designing for people:
•Example airplane errors:
–If booster pump fails, turn on fuel valve within 3 seconds –Tests showed it took at least five seconds to actually ll d do i it! !
•Result
–Human factors became critically important
Differences Between The Designer g And Operator
Darn these hooves! I h hit t the wrong sw switch tch again! aga n! Who designs these instrument panels, raccoons?
The human
• Information i/o …
– visual, auditory, haptic, movement
• Information stored in memory
– se sensory, so y, short-term, s o t te , long-term o g te
• Information processed and applied
– reasoning, reasoning problem solving, solving skill, skill error
• Emotion influences human capabilities • Each E h person is i different diff t
Core cognitive aspects
• Attention • Perception and recognition • Memory • Reading, g, speaking p g and listening g • Problem-solving, planning, reasoning and decision-making decision making, learning
Vision
Two stages in vision • physical reception of stimulus • processing and interpretation of stimulus
The Eye - physical reception
• mechanism for f receiving light and transforming it into electrical energy • light l h reflects fl f from objects b • images are focused upside-down on retina • retina contains rods for low light vision and d cones f for color l vision i i • ganglion cells (brain!) detect pattern and d movement
Interpreting the signal
• Size and depth
– visual angle indicates how much of view object b occupies
(relates to size and distance from eye)
– visual i l acuity it i is the th ability bilit t to perceive i d detail t il
(limited)
– familiar objects perceived as constant size
(in spite of changes in visual angle when far away)
– cues like overlapping pp g help pp perception p of size and depth
Interpreting the signal (cont)
• Brightness h
– – – – subjective reaction to levels of light affected by luminance of object measured by just noticeable difference visual acuity increases with luminance as does flicker made up of hue, intensity, saturation cones sensitive to color wavelengths blue acuity is lowest 8% males and 1% females color blind
• Color
– – – –
color and 3D
• both often used very badly! • color
– – – – older monitors limited palette color over used because ‘it is there’ beware color blind! use sparingly to reinforce other information
• 3D effects
– good for physical information and some graphs – but if over used … e.g. text in perspective!! 3D pie charts
bad use of color
• over use site) without very good reason (e.g. kids’
• colour blindness • poor use of contrast • do adjust your set!
– adjust your monitor to greys only – can you still read your screen?
Interpreting the signal (cont)
• The visual system compensates for:
– movement – changes in luminance.
• Context is used to resolve ambiguity • Optical illusions sometimes occur due to over compensation
Optical Illusions
the Ponzo illusion
the Muller Lyer illusion
Reading
• Several l stages:
– visual pattern perceived – decoded using internal representation of language – interpreted using knowledge of syntax, semantics, pragmatics
• • • •
Reading involves saccades and fixations Perception occurs during fixations Word shape is important to recognition Negative g contrast improves p reading g from computer screen
Hearing
• Provides d information f about b environment:
distances, directions, objects etc.
• Physical apparatus:
– outer ear – protects inner and amplifies sound – middle ear – transmits sound waves as – inner ear
vibrations to inner ear – chemical transmitters are released and cause impulses in auditory nerve
• Sound
– pitch – loudness – timbre – sound frequency – amplitude – type or quality
Hearing (cont)
• Humans can hear frequencies from 20Hz to 15kHz
– l less accurate t distinguishing di ti i hi high hi h f frequencies i th than low.
• Auditory system filters sounds
– can attend to sounds over background g noise.
Touch
• Provides important feedback about environment. • May be key sense for someone who is visually impaired. • Stimulus received via receptors in the skin:
– thermoreceptors – nociceptors – mechanoreceptors – heat and cold – pain – pressure
(some instant, some continuous)
• Some areas more sensitive than others e.g. fingers. • Kinethesis - awareness of body position
– affects comfort and performance.
Movement
• Time taken k to respond d to stimulus: l reaction time + movement time • Movement time dependent on age, fitness etc. • Reaction time - dependent on stimulus type:
– visual ~ 200ms – auditory ~ 150 ms – pain ~ 700ms
Movement (cont)
• Fitts' ' Law describes d b the h time taken k to hit h a screen target: Mt = a + b log2(D/S + 1)
where: a and b are empirically p y determined constants Mt is movement time D is Distance S is Si Size e of target ta get
? targets as large as possible distances as small as possible
Att ti Attention
• Selecting things to concentrate on from the mass around us, at a point in time • F Focussed d and d divided di id d attention tt ti enables bl us to t b be selective in terms of the mass of competing stimuli but limits our ability to keep track of all events
– magicians use this h to their h advantage! d
• Information at the interface should be structured to capture users users’ attention attention, e e.g. g use perceptual boundaries (windows), color, reverse video, sound and flashing lights
Design implications for attention
• Make information salient when it needs attending to • Use techniques that make things stand out like color, ordering, d i spacing, i underlining, d li i sequencing i and d animation • Avoid cluttering the interface - follow the google.com google com example of crisp, simple design • Avoid using too much because the software allows it
An example of over-use of graphics
Our Situation
? State St t
the th bad b d news ? Be clear, don’t try to obscure the situation
Perception and recognition
• How information is acquired from the world and transformed into experiences • Obvious implication is to design representations that are readily perceivable, g e.g.
– Text should be legible – Icons should be easy to distinguish and read
Which is easiest to read and why?
What is the time?
What is the time?
What is the time?
What is the time?
What is the time?
Memory
There are three types of memory function: Sensory memories Sh t t Short-term memory or working ki memory
Long-term memory
Memory
• I Involves l encoding di and d recalling lli k knowledge l d and d acting ti appropriately don t remember everything - involves filtering and • We don’t processing • Context is important in affecting our memory • We recognize things much better than being able to recall things
– The rise of the GUI over command-based interfaces
• Better at remembering images than words
– The use of icons rather than names
sensory memory
• Buffers for stimuli received through senses
– iconic memory: visual stimuli – echoic memory: aural stimuli – haptic memory: tactile stimuli
• Example a pe
– stereo sound
• Continuously overwritten
Short term memory (STM) Short-term
• Scratch-pad for temporary recall
– rapid id access ~ 70ms 70 – rapid decay ~ 200ms – limited capacity p y - 7± 2 chunks
Examples
212348278493202 0121 414 2626 HEC ATR ANU PTH ETR EET
The problem with the classic ‘7 7±2 2’
• George Miller’s Miller s theory of how much information people can remember • People People’s s immediate memory capacity is very limited • Many designers have been led to believe that this is useful finding g for interaction design g
Wh t some designers What d i get t up to… t
• • • • • Present only 7 options on a menu Display only 7 icons on a tool bar Have no more than 7 bullets in a list Place only 7 items on a pull down menu Place only 7 tabs on the top of a website page
– But this is wrong? Why?
Wh ? Why?
• Inappropriate I i t application li ti of f th the th theory • People can scan lists of bullets, tabs, menu items till they see the one they want • They don’t have to recall them from memory having only briefly heard or seen them • Sometimes a small number of items is good design • But it depends on task and available screen estate
Long term memory (LTM) Long-term
• Repository for all our knowledge
– slow access ~ 1/10 second – slow l d decay, if any – huge or unlimited capacity
• Two types
– episodic – serial memory of events – semantic – structured memory of facts,concepts, skills semantic LTM derived from episodic LTM
Long term memory (cont.) Long-term (cont )
• Semantic memory structure
– provides access to information – represents t relationships l ti hi b between t bit bits of f information i f ti – supports inference
• Model: semantic network
– inheritance – child nodes inherit properties of parent nodes d – relationships between bits of information explicit – supports inference through inheritance
LTM - semantic network
Models of LTM - Frames
• Information organized in data structures • Slots in structure instantiated with values for instance of data • Type–subtype relationships
DOG
Fixed Fi d legs: 4 Default diet: carniverous sound: bark Variable size: color l
COLLIE
Fixed Fi d breed of: DOG type: sheepdog Default size: 65 cm Variable color
Models of LTM - Scripts
Model of stereotypical information required to interpret situation Script has elements that can be instantiated with values for context
Script for a visit to the vet
Entry conditions: dog ill vet open owner has money Result: dog better owner poorer vet richer examination table medicine instruments Scenes: Roles: vet examines diagnoses treats owner brings dog in pays takes dog out arriving at reception waiting in room examination paying dog needs medicine dog needs operation
Props:
Tracks:
Models of LTM - Production rules
Representation of procedural knowledge. C d Condition/action / rules l
if condition is matched then use rule to determine action.
IF dog is wagging tail THEN pat dog IF dog is growling THEN run away
LTM - Storage of information
• rehearsal
– information moves from STM to LTM
• total time hypothesis
– amount retained proportional to rehearsal time
• distribution of practice effect
– optimized p by y spreading p g learning g over time
• structure, meaning and familiarity
– information easier to remember
LTM - Forgetting
decay
– information is lost gradually but very slowly
interference
– new information replaces old: retroactive interference – old may interfere with new: proactive inhibition so may not forget at all memory is selective … … affected by emotion – can subconsciously `choose' to forget
LTM - retrieval
recall
– information reproduced from memory can be assisted i t db by cues, e.g. categories, t i imagery i
recognition
– information gives knowledge that it has been seen before – less complex than recall - information is cue
Thinking
Reasoning
deduction, induction, abduction
Problem solving
Deductive Reasoning
• Deduction: d
– derive logically necessary conclusion from given premises. p e.g. If it is Friday then she will go to work It is Friday Therefore she will go to work. work
Deduction (cont.) (cont )
• When truth and logical validity clash …
e.g. Some people are babies Some babies cry Inference - Some people cry
Correct?
Inductive Reasoning
• Induction: d
– generalize from cases seen to cases unseen e g all elephants we have seen have trunks e.g. therefore all elephants have trunks.
• Unreliable:
– can only prove false not true
… but useful! • Humans not good at using negative evidence
– e.g. Wason’s cards
Wason's Wason s cards
7 E 4 K
If a card has a vowel on one side it has an even number on the other Is this true? How many cards do you need to turn over to find out? …. and which cards?
Abductive reasoning
• reasoning from event to cause
e.g. Sam drives fast when drunk. If I see Sam driving fast, assume drunk.
• Unreliable:
– can lead to false explanations p
Problem solving
• Process of f finding f d solution l to unfamiliar f l task k using knowledge. • Several theories. • Gestalt
– problem solving both productive and reproductive – productive draws on insight and restructuring of problem – attractive but not enough evidence to explain `insight' insight' etc. – move away from behaviourism and led towards information processing theories
Problem solving (cont.) (cont )
Problem space theory
– problem space comprises problem states – problem bl solving l i i involves l generating ti states t t using i l legal l operators – heuristics may y be employed p y to select operators p e.g. means-ends analysis – operates within human information processing system e g STM limits etc. e.g. etc – largely applied to problem solving in well-defined areas e.g. puzzles rather than knowledge intensive areas
Problem solving (cont.) (cont )
• Analogy l
– analogical mapping:
• novel p problems in new domain? • use knowledge of similar problem from similar domain
– analogical mapping difficult if domains are semantically different
• Skill acquisition
– skilled activity characterized by chunking
• lot of information is chunked to optimize STM
– conceptual rather than superficial grouping of problems – information is structured more effectively
Errors and mental models
Types of f error • slips p
– right intention, but failed to do it right – causes: poor physical skill,inattention etc. – change to aspect of skilled behaviour can cause slip
• mistakes
– wrong intention – cause: incorrect understanding
humans create mental models to explain p behaviour. if wrong (different from actual system) errors can occur
Mental models
• Users develop an understanding of a system through learning & using it • Knowledge is often described as a mental model
– How to use the system (what to do next) – What to do with unfamiliar systems or unexpected situations (how the system works)
• P People l make k inferences i f using i mental l models d l of f how to carry out tasks
M t l models Mental d ls
• Craik (1943) described mental models as internal constructions of some aspect of the external world enabling predictions to be made • Involves unconscious and conscious processes, where images and analogies are activated • Deep versus shallow models (e.g. how to ) drive a car and how it works)
Everyday reasoning & mental models
(a) You arrive home on a cold winter’s night to a cold house. How do you get the house to warm up as quickly as possible? poss b e Set Se the e thermostat e os a to o be at a its s highest g es or o to o the e desired temperature? (b) You arrive home starving hungry hungry. You look in the fridge and find all that is left is an uncooked pizza. You have an electric oven. Do you warm it up to 375 degrees first and then put it in (as specified by the instructions) or turn the oven up higher to try to warm it up quicker?
Heating g up p a room or oven that is thermostat-controlled
• Many people have erroneous mental models (Kempton, 1996) • Why?
– General valve theory, where ‘more is more’ principle i generalised is li d to t different diff t settings tti (e.g. ( gas pedal, d l gas cooker, tap, radio volume) – Thermostats based on model of on-off switch model
Heating g up p a room or oven that is thermostat-controlled
• Same is often true for understanding how interactive devices and computers work:
– P Poor, often ft incomplete, i l t easily il confusable, f bl based b d on inappropriate analogies and superstition (Norman, 1983) – e.g. frozen cursor/screen - most people will bash all manner of keys
External cognition
• Concerned with explaining how we interact with external representations (e.g. maps, notes, , diagrams) g ) • What are the cognitive benefits and what processes involved • How they extend our cognition • What computer-based representations can we develop to help even more?
Externalizing g to reduce memory y load
• Diaries, reminders,calendars, notes, shopping lists, to-do lists - written to remind us of what to do • Post-its, piles, marked emails - where placed indicates priority of what to do • External representations:
– Remind us that we need to do something (e.g. to buy something g for mother’s day) y) – Remind us of what to do (e.g. buy a card) – Remind us when to do something (e.g. send a card by a certain date) )
Computational offloading
• When a tool is used in conjunction with an external representation to carry out a computation (e.g. pen and paper) ) • Try doing the two sums below (a) in your head, (b) on a piece of paper and c) with a calculator.
– 234 x 456 =?? – CCXXXIIII x CCCCXXXXXVI = ???
• Which is easiest and why? Both are identical sums
Annotation i and d cognitive i i tracing i
• Annotation involves modifying existing representations through making marks
– e.g. crossing i off, ff ticking, ti ki underlining d li i
• Cognitive tracing involves externally manipulating items into different orders or structures
– e.g. playing scrabble, playing cards
Emotion
• Various theories of how emotion works
– James-Lange: g emotion is our interpretation p of a physiological response to a stimuli – Cannon: emotion is a psychological response to a stimuli – Schacter-Singer: emotion is the result of our evaluation of our physiological responses, in the light of the whole situation we are in
• Emotion clearly involves both cognitive and physical responses to stimuli
Emotion (cont.) (cont )
• The biological response to physical stimuli is called affect • Affect influences how we respond p to situations
– positive ? creative problem solving – negative ? narrow thinking
“Negative affect can make it harder to do even easy tasks; positive affect can make it easier to do difficult tasks”
(Donald Norman)
Emotion (cont.) (cont )
• Implications for interface design
– stress will increase the difficulty of problem solving – relaxed users will be more forgiving of shortcomings h i i in d design i – aesthetically pleasing and rewarding interfaces will increase positive affect
Individual differences
• long term – gender, physical and intellectual abilities • short h t term t – effect of stress or fatigue • changing – age Ask yourself: will design decision exclude section of user population? l ti ?
Psychology y gy and the Design g of Interactive System
• Some S direct di applications li i
– e.g. blue acuity is poor ? blue should not be used for important detail
• However, correct application generally requires g of context in p psychology, y gy, and an understanding understanding of particular experimental conditions
Involving users in the design
• At the very least, talk to users
– It It’s s surprising how many designers don’t!
• Contextual Inquiries
– Interview users in their usage place l ( (e.g., office), ff ) during d i their h i normal routine (e.g., while working) k ) – Used to discover user’s culture, requirements, expectations, etc.
Involving users in the design
• Create prototypes
– It It’s s hard to comment on something that doesn’t yet exist – Users are good at giving feedback for something that is even partially built
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