cs422 - human computer interaction
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CS422 - Human Computer Interaction. Instructor: Mehwish Aziz Spring: Fall 2010 Lecture 4-6. CHAPTER – 1 HUMAN. Model Human Processor. Way back in 1983, Card, Moran and Newell gave a Model Human Processor - PowerPoint PPT PresentationTRANSCRIPT
CS422 - Human Computer Interaction
Instructor: Mehwish AzizSpring: Fall 2010Lecture 4-6
CHAPTER – 1HUMAN
Model Human Processor• Way back in 1983, Card, Moran and Newell gave a Model Human Processor
- Simplified view of human processing involved on interaction with computer system. This view comprises of:
Perceptual System (Input-Output) – handling sensory stimulus from outside world
Motor system (Memory) – controlling actionsCognitive system (Processing) – providing processing required for the
two
• Inspired from the above analogy, we consider today human user as information processing system
• External factors like social and organizational environment
• Moving ahead – let’s see what we will cover on ‘HUMAN’
Outline• How Limited Capacity to process information is a major
implication for design?
• Limited Capacity as Human possess:Limited numbers of receivable and reception
channelsLimited Memory Varying criteria to process and apply informationEmotions
Outline
• Limited numbers of receivable and reception channelsvisual channel auditory channel movement haptic channel
• Limited Memory sensory memory short-term (working) memory long-term memory
Outline• Varying criteria to process and apply information:
reasoning problem solving skill acquisition error
• Emotion influences human capabilities
• Users share common capabilities but are individuals with differences, which should not be ignored.
Input-Output Channels• Input-Output Channels of Human:
Input Channels – SensesOutput Channels – Motor control of the effectors
• Out of all senses – Vision, Hearing and Touch are major ones for HCI
• Effectors – limbs, fingers, eyes, head and vocal system
Input-Output Channels• Simplest Example – when you use PCs
Sight to view informationTouch to prompt input to PC through h/w interfaceHearing – when a system beeps on your mistakeVocals – when giving a command through speech or
say video presentation
• Is computers Interaction today on a balance for both disabled and normal human?
Human Vision• Vision has two stages
Physical reception of stimulusProcessing and interpretation of stimulus
• Physical Reception of stimulusMechanisms for receiving light and transforming it into
electrical energyLight reflects from objectsImages are focused upside-down on retinaRetina contains rods for low light vision and cones for
color visionGanglion cells (brain!) detect pattern and movement
Processing and Interpretation of Stimulus• Identification of Size & Depth
Visual angle indicates how much of view object occupies (relates to size and distance from eye)
Visual Acuity is ability to perceive details (limited)
Familiar objects perceived as constant size (in spite of changes in visual angle when far away)
Cues like overlapping help perception of size and depth
Processing and Interpretation of Stimulus• Brightness
Subjective reactions to levels of lightAffected by luminance of objectsMeasured by just noticeable differencesVisual Acuity increases with luminance as does flicker
• ColorComposed of hew, intensity and saturationCones sensitive to color wavelengthsBlue Acuity is lowestColor Blindness - 8% Males and 1% Females
Processing and Interpretation of Stimulus
• Visual Systems 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
Is this text Correct?
the quick brown fox jumps over the
the lazy dog
Design Focus• Optical Illusion highlight the difference between way things are
and way we perceive them
• In interface design we need to be aware that we will not perceive things exactly as they are!
• Optical Illusion also affects page symmetry
• In graphic design there is a phenomena known as optical center saying that See the center of page a little above than actual centerBottom page margins tend to be increased by 50% to
compensate incase page is arranged by actual center
Reading• Reading is performed with certain stages
Visual Patterns perceivedDecoded using internal representation of language Interpreted using knowledge of syntax, semantics, and pragmatics
• Reading involves saccades and fixations
• Perceptions occurs during fixations
• Word shape is important to recognition
• Negative contrast improves reading from computer screen
• For negative contrasts - Lets review some web-pages
The question persists and indeedgrows whether the computer will makeit easier or harder for human beings to
know who they really are, to identifytheir real problems, to respond more
fully to beauty, to place adequate valueon life, and to make their world safer
than it now is.
Norman Cousins – The Poet and the Computer, 1966
The question persists and indeedgrows whether the computer will make
it easier or harder for human beings toknow who THEY REALLY ARE, TO IDENTIFYTHEIR REAL PROBLEMS, to respond morefully to beauty, to place adequate value
on life, and to make their world saferthan it now is.
Norman Cousins – The Poet and the Computer, 1966
Hearing• Provides information about environment
distances, directions, objects etc.
• Physical apparatus:outer ear – protects inner ear and amplifies soundmiddle ear – transmits sound waves as vibrations to inner earinner ear – chemical transmitters are released and cause
impulses in auditory nerve
• SoundPitch – sound frequencyloudness – amplitudeTimbre – type or quality
Hearing• Humans can hear frequencies from 20Hz to 15kHz
less accurate distinguishing high frequencies than low
• Auditory system filters sounds can attend to sounds over background noise
for example, the cocktail party phenomenon
• Different applications are using sound speech toconvey information or generate requests for user
commands
Hearing• Uses of non-speech sound include the following:
Attention – to attract user’s attention to an alarming state or end of the process
Status Information – continuous background sounds can be used to convey status information especially where continuous visual attention is difficult
Confirmation – a sound with an action to confirm that the action has been carried out
Navigation – using changing sound to indicate where the user is in a system say a sound to support navigation hypertext
Touch• Provides important feedback about environment
• Can be a key sense for one who is visually impaired
• Stimulus received via the following receptors in the skin Thermo-receptors – heat and coldNociceptors – painMechanoreceptors – pressure (some instant or
continuous)
• Some areas are more sensitive than others e.g. fingers
Touch• Kinaesthesia - awareness of body position
affects comfort and performance
• E-Commerce seems to be very successful when it comes to shop for travel services, books and Computer accessories/ Softwares ….. What about clothes shopping through e-commerce? Do
you know about TouchCity?
Movement• Time taken to respond to stimulus say hitting a button in response to
a questionreaction time + movement time
• Reaction time depends on informationReceived by sensory receptors transmitted to brainBrain’s processing to generate a response
• Movement time is dependent on age, fitness etc.
• Reaction time - depends on stimulus type Visual ~ 200ms Auditory ~ 150 ms Pain ~ 700ms
Movement• Increasing reaction time decreases accuracy only in the
unskilled operator
• How pie chart-shaped menus are preferable to list since all options are equidistant?
• Fitts' Law describes the time taken to hit a screen targetMt = a + b log2(D/S + 1)
Here; a and b are empirically determined constantsMt -> movement time, D -> Distance , S -> Size of target
=> targets as large as possible distances as small as possible
Touch + Movement• Haptics is the science of applying tactile sensation to human
interaction with computers.
• Haptic device is one that involves physical contact between the computer and the user
This enables human to feed information to computer & also receive information through felt sensation on some part of the body – Haptic Interface
Through an input/output device, such as a joystick or data gloves, that senses the body's movements
For example, in a virtual reality environment, a user can pick up a virtual tennis ball using a data glove
Memory• There are three types of memory function:
Sensory memories (Iconic, Echoic, Haptic)
Short-term memory or working memory
Long-term memory
Sensory Memory• Buffers for stimuli received through senses
iconic memory: visual stimuli echoic memory: aural stimuli haptic memory: tactile stimuli
• Examples“sparkler” trail / fireworks persistent imagestereo sound / ascertain the direction of sound origin
• Continuously overwritten or lost
Short Term Memory (STM)• Scratch-pad for temporary recall
rapid access ~ 70msrapid decay ~ 200mslimited capacity - 7± 2 chunksExamples
212348278493202
0121 414 2626
HEC ATR ANU PTH ETR EET (move last to one)
Long Term Memory (LTM)• Repository for all our knowledge
slow access ~ 1/10 secondslow decay, if anyhuge or unlimited capacity
• Two typesEpisodic – serial memory of eventsSemantic – structured memory of facts , concepts, skills -> derived from episodic memory based
experiences
• semantic LTM derived from episodic LTM
Long Term Memory (LTM)• Semantic memory structure
provides access to informationrepresents relationships between bits of
informationsupports inference (deductions)
• Model: semantic networkinheritance – child nodes inherit properties of parent
nodesrelationships between bits of information is explicitsupports inference through inheritance
LTM – Semantic Network
Models of LTM - Frames• Information organized in data structures using slots and
frames• Slots in structure instantiated with values for instance of data• Frames slots may contain default, fixed or variable
information• Type–subtype relationships DOG Fixed legs: 4
Default diet: carnivorous sound: bark
Variable size: color:
COLLIE Fixed 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• “John took his dog to the surgery. After seeing the web , he left.”
Script for a visit to the vetEntry conditions: dog ill
vet openowner has money
Result: dog betterowner poorervet richer
Props: examination tablemedicineinstruments
Roles: vet examines diagnoses treatsowner brings dog in pays takes dog out
Scenes: arriving at receptionwaiting in roomexaminationpaying
Tracks: dog needs medicinedog needs operation
Models of LTM – Production Rules• Representation of procedural knowledge• Condition/action rules
if condition is matchedthen use rule to determine action
IF dog is wagging tailTHEN pat dog
IF dog is growlingTHEN run away
LTM – Storage of Information• rehearsal
information moves from STM to LTM
• total time hypothesisamount retained proportional to rehearsal time
• distribution of practice effectoptimized by spreading learning over time
• structure, meaning and familiarityinformation easier to remember
LTM - Forgetting• decay
information is lost gradually but very slowly
• interferencenew information replaces old: retroactive interferenceold 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 by cues, e.g. categories, imagery
• recognitioninformation gives knowledge that it has been seen
beforeless complex than recall - information is cue
Thinking - Reasoning• Reasoning
deduction, induction, abduction• Deduction: derive logically necessary conclusion from given
premisese.g. If it is Friday then she will go to workIt is FridayTherefore she will go to work.
• Logical conclusion not necessarily true:e.g. If it is raining then the ground is dryIt is rainingTherefore the ground is dry
Thinking - Reasoning• Deduction: When truth and logical validity clash …
e.g. Some people are babiesSome babies cry
• Inference - Some people cry• Correct?
• Induction: generalize from cases seen to cases unseen e.g. all elephants we have seen have trunkstherefore 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.
Thinking - Reasoning• Abductive Reasoning: reasoning from event to
causee.g. Sam drives fast when drunk.
If I see Sam driving fast, assume drunk.
• Unreliable: can lead to false explanations
Thinking – Problem Solving• Process of finding solution to unfamiliar task using
knowledge.
• Several theories exist.
• Gestalt Theory:problem solving both productive and reproductiveproductive draws on insight and restructuring of problemattractive but not enough evidence to explain `insight' etc.move away from behaviourism and led towards information
processing theories
Thinking – Problem Solving• Problem space theory:
problem space comprises problem statesproblem solving involves generating states using legal
operatorsheuristics may be employed to select operators
e.g. means-ends analysisoperates within human information processing system
e.g. STM limits etc.largely applied to problem solving in well-defined areas
e.g. puzzles rather than knowledge intensive areas
Thinking – Problem Solving• Analogy
analogical mappingnovel problems in new domainuse knowledge of similar problem from similar domain analogical mapping difficult if domains are semantically
different
• Skill acquisitionskilled activity characterized by chunkinglot of information is chunked to optimize STMconceptual rather than superficial grouping of problemsinformation is structured more effectively
Errors & Mental Models• Slips
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 understandinghumans create mental models to explain behaviour.if wrong (different from actual system) errors can occur
Emotion• Various theories of how emotion works
James-Lange: emotion is our interpretation of a physiological response to a stimuli
Cannon: emotion is a psychological response to a stimuliSchacter-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• The biological response to physical stimuli is called
affect
• Affect influences how we respond to situationspositive creative problem solvingnegative 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 + Individual Differences• Implications for interface design
Stress: increase difficulty of problem solvingRelaxed users: more forgiving of shortcomings in designaesthetically pleasing and rewarding interfaces: increase
positive affect
• Individual Differences:long term: sex, physical and intellectual abilitiesshort term: effect of stress or fatigueChanging: age
• Ask yourself: will design decision exclude section of user population?
Psychology & Designing Interactive Design• Some direct applications
e.g. blue acuity is poor blue should not be used for important detail
• However, correct application generally requiresunderstanding of context in psychology, understanding of particular experimental conditions
• A lot of knowledge has been distilled in:guidelines (chap 7)cognitive models (chap 12)experimental and analytic evaluation techniques (chap 9)
CHAPTER – 2COMPUTER
Computers • Computers consisting of I/O Devices, memory and processing – just
like human being.• Richer Interaction everywhere and everywhen!
sensorsand deviceseverywhere
Text Entry Devices• keyboards (QWERTY et al.):
QWERTY arrangement not optimal for typinglayout to prevent typewriters jamming!
Alternative designs allow faster typing but large social base of QWERTY typists produces reluctance to change.
• Alternative - Alphabetic: keys arranged in alphabetic ordernot faster for trained typistsnot faster for beginners either!
2 3 4 5 6 7 8 9 0Q W E R T Y U I
1O P
S D F H J LA G K
Z X C V B N M , .SPACE
Text Entry Devices• Dvorak
common letters under dominant fingers, biased for right handcommon combinations of letters alternate between hands10-15% improvement in speed and reduction in fatigueStill, large social base of QWERTY typists produce market
pressures not to change• Special Keyboards: for one handed use e.g. Maltron left-handed
keyboard
Text Entry Devices• Chord keyboards: only a few keys - four or 5
letters as combination of key presses compact size - ideal for portable
applications short learning time – key presses reflect
letter shape Fast - once you have trained Social resistance still exists, plus fatigue
after extended use
Text Entry Devices• Phone pads:
use numeric keys with multiple presses
surprisingly fast!
• T9 predictive entrytype as if single key for
each letteruse dictionary to ‘guess’
the right wordbut 26 -> ‘am’ or ‘an’ etc.
Text Entry Devices• Handwriting Recognition:
Text can be input into the computer, using a pen and a digesting tablet
natural interactionTechnical problems:
capturing all useful information - stroke path, pressure, etc. in a natural manner
segmenting joined up writing into individual lettersinterpreting individual letterscoping with different styles of handwriting
Used in PDAs, and tablet computers etc.
Text Entry Devices• Speech Recognition:
Improving rapidlyMost successful when:
single user – initial training and learns peculiaritieslimited vocabulary systems
Problems withexternal noise interferingimprecision of pronunciationlarge vocabulariesdifferent speakers
Positioning, Pointing & Drawing• Mouse: Handheld pointing device: very common, easy to use
Two characteristics: planar movement, buttons
Mouse located on desktop: requires physical space, no arm fatigue
Relative movement only is detectable.
Movement of mouse moves screen cursor
Screen cursor oriented in (x, y) plane, mouse movement in (x, z) plane …
Positioning, Pointing & Drawing• Mouse: Two methods for detecting motion:• Mechanical:
Ball on underside of mouse turns as mouse is movedRotates orthogonal potentiometersCan be used on almost any flat surface
• Optical:light emitting diode on underside of mousemay use special grid-like pad or just on deskless susceptible to dust and dirtdetects fluctuating alterations in reflected light intensity
to calculate relative motion in (x, z) plane
Positioning, Pointing & Drawing• Mouse: some experiments with the foot-mouse
controlling mouse movement with feet …not very common but foot controls are common elsewhere:
car pedalssewing machine speed controlorgan and piano pedals
Touchpad• Small touch sensitive tablets:
‘stroke’ to move mouse pointerused mainly in laptop computers
• Good ‘acceleration’ settings importantfast stroke
lots of pixels per inch movedinitial movement to the target
slow strokeless pixels per inchfor accurate positioning
Trackball & Thumbwheels• Trackball
ball is rotated inside static housinglike an upside down mouse!
relative motion moves cursorindirect device, fairly accurateseparate buttons for pickingvery fast for gamingused in some portable and notebook computers.
• Thumbwheels …for accurate CAD – two dials for X-Y cursor positionfor fast scrolling – single dial on mouse
Touch Sensitive Screen• Detect the presence of finger or stylus on the screen
works by interrupting matrix of light beams, capacitance changes or ultrasonic reflections
direct pointing device
• Advantages: fast, and requires no specialised pointergood for menu selection suitable for use in hostile environment: clean and safe from damage
• Disadvantages:finger can mark screen imprecise (finger is a fairly blunt instrument!)
difficult to select small regions or perform accurate drawing lifting arm can be tiring
Stylus & Light Pen• Stylus
small pen-like pointer to draw directly on screenmay use touch sensitive surface or magnetic detectionused in PDA, tablets PCs and drawing tables
• Light Pennow rarely useduses light from screen to detect location
• BOTH …very direct and obvious to usebut can obscure screen
Digitizing Tablet• Mouse like-device with cross hairs
• used on special surface - rather like stylus
• very accurate- used for digitizing maps
Eye Gaze• control interface by eye gaze direction
e.g. look at a menu item to select it
• uses laser beam reflected off retina… a very low power laser!
• mainly used for evaluation
• potential for hands-free control
• high accuracy requires headset
• cheaper and lower accuracy devices available….sit under the screen like a small webcam
Cursor Keys• Four keys (up, down, left, right) on keyboard• Extremely cheap, but slow. • Useful for not much more than basic motion for
text-editing tasks• No standardised layout, but inverted “T”, most
common
Discrete Positioning Controls• phones, TV controls etc.
cursor pads or mini-joysticksdiscrete left-right, up-downmainly for menu selection
Display Devices• Bitmap Displays:
screen is vast number of coloured dots
Resolution and Color Depth• Resolution used (inconsistently) for
number of pixels on screen (width x height)e.g. SVGA 1024 x 768, PDA perhaps 240x400
density of pixels (in pixels or dots per inch - dpi)typically between 72 and 96 dpi
• Aspect ratioRatio between width and height4:3 for most screens, 16:9 for wide-screen TV
• Colour depthhow many different colours for each pixelblack/white or greys only8 bits each for red/green/blue = millions of colours256 from a palette
Anti-Aliasing• Jaggies
diagonal lines that have discontinuities due to horizontal faster scan process
• Solution to jaggies is Anti-aliasingsoftens edges by using shades of line colourused for text
Cathode Ray Tubes
• Cheap display device • Fast response time for rapid animation coupled with
high colour capability• Fairly bulky in comparison to flatter displays• Stream of electrons emitted from electron gun, • focused and directed by magnetic fields,• used in TVs and computer monitors• View has a high rate of flicker• Way of reducing flicker from screen
Higher scan ratesInterlacing – tracing first all odd then even lines
Liquid Crystal Display• Liquid Crystal Display:
Smaller, lighterFound on portables and notebooks … and increasingly on desktop
and even for home TVUsed in dedicated displays: digital watches, mobile phonesRequires refreshing at usual rates but slow response to the crystals
Flicker isn’t usually noticeableHow it works:
Top plate transparent and polarised, bottom plate reflecting.Light passes through top plate and crystal, and reflects back to
eye. Voltage applied to crystal changes polarisation and hence colourN.B. light reflected not emitted => less eye strain
Special Displays• Random Scan (Directed-beam refresh, vector
display)draw the lines to be displayed directlyno jaggieslines need to be constantly redrawnrarely used except in special instruments
• Direct view storage tube (DVST)Similar to random scan but persistent => no flickerCan be incrementally updated but not selectively erasedUsed in analogue storage oscilloscopes
Large Displays• Large Displays - used for meetings, lectures, etc.• Technology used is:
plasma – usually wide screen video walls – lots of small screens together projector – RGB lights or LCD projectorhand/body obscures screenmay be solved by 2 projectors + clever software back-projectedfrosted glass + projector behind
Situated Display• displays in ‘public’ places
large or smallvery public or for small group
• display only - for information relevant to location• interactive - use stylus, touch sensitive screen• in all cases … the location matters
meaning of information or interaction is related to the location
Hermes – A Situated Display
small displaysbeside
office doors
handwrittennotes left
using stylusoffice ownerreads notes
using web interface
Digital Paper• what?
thin flexible sheetsupdated electronicallybut retain display
• how?small spheres turned orchannels with coloured liquid
and contrasting spheresrapidly developing area
appearance
crosssection
Virtual Reality and 3D Interaction
• Positioning in 3D Space:cockpit and virtual controls
steering wheels, knobs and dials … just like real!3D mouse
six-degrees of movement: x, y, z + roll, pitch, yaw data glove
fibre optics used to detect finger positionVR helmets
detect head motion and possibly eye gazewhole body tracking
accelerometers strapped to limbs or reflective dots and video processing
Virtual Reality and 3D Interaction
pitch
yaw
roll
Pitch, Yaw & Roll
Virtual Reality and 3D Interaction
• 3D Displaysdesktop VR
ordinary screen, mouse or keyboard controlperspective and motion give 3D effect
seeing in 3Duse stereoscopic visionVR helmetsscreen plus shuttered specs, etc.
• VR Headsets – 3D Effectssmall TV screen slightly different angles
Virtual Reality and 3D Interaction• VR Motion Sickness:
time delaymove head … lag … display movesconflict: head movement vs. eyes
depth perceptionheadset gives different stereo distancebut all focused in same planeconflict: eye angle vs. focus
conflicting cues => sicknesshelps motivate improvements in technology
Virtual Reality and 3D Interaction• Simulators and VR Caves
scenes projected on wallsrealistic environmenthydraulic rams!real controlsother people