18 cse366t human computer interaction - hci - unit i

4/6/2022 SRM University Ramapuram 1
8/22/2011
School of Computing, Department of IT 1
Human Computer
Interaction – 18CSE366T
UNIT - I
Mrs. S. Babeetha
AP(Sr.G)
SRMIST, Ramapuram

the human
1. Human Computer Interaction by Alan Dix, Janet Finlay,
Gregory D.Abowd and Russell Beale – Third Edition - Pearson
Education – 2004
2. Human Computer Interaction by K.Meena and R.Sivakumar –
2015 – Prentice Hall India
3. Designing the User Interface: Strategies for Effective Human
Computer Interaction by Ben Shneiderman and Catherine
Plaisant – Fifth Edition - 2009 – Pearson Addison Wesley
4. Designing Web Interfaces by Bill Scott and Theresa Neil –
First Edition – O‘Reilly Media Inc. – 2009
5. Mobile Design and Development by Brian Fling - First Edition
– O‘Reilly Media Inc. – 2009

Human Computer Interaction

• Human Computer interaction (HCI) is characterized as a dialogue or
interchange between the human and the computer because the
output of one serves as the input for the other in an exchange of
actions and intentions.
• HCI is the study of interaction between people (users) and
computers.
• Human Computer Interaction is concerned with the design,
evaluation and implementation of interactive computing systems for
human use and with the study of major phenomena surrounding
them.
• Human Computer Interaction (HCI) is an interdisciplinary field in
which computer scientists, engineers, psychologists, social scientists
and design professional play important roles.
Human Computer Interaction (HCI)

• HCI tackles questions concerning how people interact with
computers
• ◦ Are computers intuitive or complicated?
• ◦ Are computers rewarding or frustrating?
• ◦ How can computers be made accessible to everybody (e.g.
different physical abilities, different languages etc.)?
• ◦ To what level can computer interaction be standardized?
• ◦ Are computers “user-friendly”?
• ◦ What does it mean to be “user-friendly”?
Introduction

• The goal of HCI is to improve the interaction between users and
computers by making computers more user- friendly and
receptive to the user's needs.
• Interacting with technology is cognitive.
• Human information processing referred to as cognition
• Human cognition process is involved when interacting with
system, like attention, perception and recognition, memory,
learning, reasoning, problem solving and decision making.
• Need to take into account cognitive processes involved and
cognitive limitations of users.
• Provides knowledge about what users can and cannot be
expected to do.
Introduction

 Information i/o …
 visual, auditory, haptic, movement
 Information stored in memory
 sensory, short-term, long-term
 Information processed and applied
 reasoning, problem solving, skill, error
 Emotion influences human capabilities
 Each person is different

Two stages in vision
• physical reception of stimulus
• processing and interpretation of stimulus

 mechanism for receiving light and
transforming it into electrical energy
 light reflects from objects
 images are focused upside-down on retina
 retina contains rods for low light vision
and cones for colour vision
 ganglion cells (brain!) detect pattern and
movement

 Size and depth
 visual angle indicates how much of view object
occupies
(relates to size and distance from eye)
 visual acuity is ability to perceive detail (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

 Brightness
 subjective reaction to levels of light
 affected by luminance of object
 measured by just noticeable difference
 visual acuity increases with luminance as does flicker
 Colour
 made up of hue, intensity, saturation
 cones sensitive to colour wavelengths
 blue acuity is lowest
 8% males and 1% females colour blind

 The visual system compensates for:
 movement
 changes in luminance
 Context is used to resolve ambiguity
 Optical illusions sometimes occur due to
over compensation

the Ponzo illusion the Muller Lyer illusion

 Several 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 contrast improves reading from
computer screen

 Provides information about environment:
distances, directions, objects etc.
 Physical apparatus:
 outer ear – protects inner and amplifies sound
 middle ear – transmits sound waves as
vibrations to inner ear
 inner ear – chemical transmitters are released
and cause impulses in auditory nerve
 Sound
 pitch – sound frequency
 loudness – amplitude
 timbre – type or quality

 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

Cocktail party phenomenon

 Provides important feedback about environment.
 May be key sense for someone who is visually
impaired.
 Stimulus received via receptors in the skin:
 thermoreceptors – heat and cold
 nociceptors – pain
 mechanoreceptors – pressure
(some instant, some continuous)
 Some areas more sensitive than others e.g. fingers.
 Kinethesis - awareness of body position
 affects comfort and performance

Braille in Elevators

 Time taken to respond to stimulus:
reaction time + movement time
 Movement time dependent on age, fitness
etc.
 Reaction time - dependent on stimulus type:
 visual ~ 200ms
 auditory ~ 150 ms
 pain ~ 700ms
 Increasing reaction time decreases accuracy
in the unskilled operator but not in the skilled
operator.

 Fitts' Law describes the time taken to hit a
screen target:
Mt = a + b log2(D/S + 1)
where: a and b are empirically determined constants
Mt is movement time
D is Distance
S is Size of target
 targets as large as possible
distances as small as possible

There are three types of memory function:
Sensory memories
Short-term memory or working memory
Long-term memory
Selection of stimuli governed by level of arousal.

 Buffers for stimuli received through senses
 iconic memory: visual stimuli
 echoic memory: aural stimuli
 haptic memory: tactile stimuli
 Examples
 “sparkler” trail
 stereo sound
 Continuously overwritten

Sparkler Trail

 Scratch-pad for temporary recall
 rapid access ~ 70ms
 rapid decay ~ 200ms
 limited capacity - 7± 2 chunks

212348278493202
0121 414 2626
HEC ATR ANU PTH ETR EET

 Repository for all our knowledge
 slow access ~ 1/10 second
 slow 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

 Semantic memory structure
 provides access to information
 represents relationships between bits of information
 supports inference
 Model: semantic network
 inheritance – child nodes inherit properties of parent
nodes
 relationships between bits of information explicit
 supports inference through inheritance

 Information organized in data structures
 Slots in structure instantiated with values for
instance of data
 Type–subtype relationships
DOG
Fixed
legs: 4
Default
diet: carniverous
sound: bark
Variable
size:
colour
COLLIE
Fixed
breed of: DOG
type: sheepdog
Default
size: 65 cm
Variable
colour

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
Props: examination table
medicine
instruments
Roles: vet examines
diagnoses
treats
owner brings dog in
pays
takes dog out
Scenes: arriving at reception
waiting in room
examination
paying
Tracks: dog needs medicine
dog needs operation

Representation of procedural knowledge.
Condition/action rules
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

 rehearsal
 information moves from STM to LTM
 total time hypothesis
 amount retained proportional to rehearsal time
 distribution of practice effect
 optimized by spreading learning over time
 structure, meaning and familiarity
 information easier to remember

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

recall
 information reproduced from memory can be assisted
by cues, e.g. categories, imagery
recognition
 information gives knowledge that it has been seen
before
 less complex than recall - information is cue

Reasoning
deduction, induction,
abduction
Problem solving

Reasoning

 Deduction:
 derive logically necessary conclusion from given premises.
e.g. If it is Friday then she will go to work
It is Friday
Therefore she will go to work.
 Logical conclusion not necessarily true:
e.g. If it is raining then the ground is wet
It is raining
Therefore the ground is wet

 When truth and logical validity clash …
e.g. Some people are babies
Some babies cry
Inference - Some people cry
Correct?
 People bring world knowledge to bear

 Induction:
 generalize from cases seen to cases unseen
e.g. all elephants we have seen have trunks
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.

Is this true?
How many cards do you need to turn over to find
out?
…. and which cards?
If a card has a vowel on one side it has an even number on the other
7 E 4 K

 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

 Process of finding solution to unfamiliar task
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' etc.
 move away from behaviourism and led towards information
processing theories

Problem space theory
 problem space comprises problem states
 problem solving involves generating states using legal
operators
 heuristics may be employed to select operators
e.g. means-ends analysis
 operates 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

 Analogy
 analogical mapping:
 novel 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

Types of error
 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 understanding
humans create mental models to explain behaviour.
if wrong (different from actual system) errors can occur

 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 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

 The biological response to physical stimuli
is called affect
 Affect influences how we respond 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)

 Implications for interface design
 stress will increase the difficulty of problem
solving
 relaxed users will be more forgiving of
shortcomings in design
 aesthetically pleasing and rewarding interfaces
will increase positive affect

 long term
– Gender, physical and intellectual
abilities
 short term
– effect of stress or fatigue
 changing
– age
Ask yourself:
will design decision exclude section of user
population?

 Some direct applications
 e.g. blue acuity is poor
 blue should not be used for important detail
 However, correct application generally requires
understanding of context in psychology, and an
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)

a computer system is made up of various elements
each of these elements affects the interaction
 input devices – text entry and pointing
 output devices – screen (small&large), digital paper
 virtual reality – special interaction and display devices
 physical interaction – e.g. sound, haptic, bio-sensing
 paper – as output (print) and input (scan)
 memory – RAM & permanent media, capacity & access
 processing – speed of processing, networks

to understand human–computer interaction
… need to understand computers!
what goes in and out
devices, paper,
sensors, etc.
what can it do?
memory, processing,
networks

 screen, or monitor, on which there are windows
 keyboard
 mouse/trackpad
 variations
 desktop
 laptop
 PDA
the devices dictate the styles of interaction that the system
supports
If we use different devices, then the interface will support a
different style of interaction
window 1
window 2
12-37pm
?

 computers in your house?
 hands up, …
… none, 1, 2 , 3, more!!
 computers in your pockets?
are you thinking …
… PC, laptop, PDA ??

in your house?
 PC
 TV, VCR, DVD, HiFi,
cable/satellite TV
 microwave, cooker,
washing machine
 central heating
 security system
can you think of more?
in your pockets?
 PDA
 phone, camera
 smart card, card
with magnetic strip?
 electronic car key
 USB memory
try your pockets and
bags

Long ago in a galaxy far away … batch processing
 punched card stacks or large data files prepared
 long wait ….
 line printer output
… and if it is not right …
Now most computing is interactive
 rapid feedback
 the user in control (most of the time)
 doing rather than thinking …
Is faster always better?

sensors
and devices
everywhere

keyboards (QWERTY et al.)
chord keyboards, phone pads
handwriting, speech

 Most common text input device
 Allows rapid entry of text by experienced
users
 Keypress closes connection, causing a
character code to be sent
 Usually connected by cable, but can be
wireless

 Standardised layout
but …
 non-alphanumeric keys are placed differently
 accented symbols needed for different scripts
 minor differences between UK and USA keyboards
 QWERTY arrangement not optimal for typing
– layout to prevent typewriters jamming!
 Alternative designs allow faster typing but large social
base of QWERTY typists produces reluctance to
change.

2 3 4 5 6 7 8 9 0
Q W E R T Y U I
1
O P
S D F H J L
A G K
Z X C V B N M , .
SPACE

Alphabetic
 keys arranged in alphabetic order
 not faster for trained typists
 not faster for beginners either!

Dvorak
 common letters under dominant fingers
 biased towards right hand
 common combinations of letters alternate between hands
 10-15% improvement in speed and reduction in fatigue
 But - large social base of QWERTY typists produce market
pressures not to change

 designs to reduce fatigue for RSI
(Repetitive Strain Injury)
 for one handed use
e.g. the Maltron left-handed keyboard

only a few keys - four or 5
letters typed as combination of keypresses
compact size
– ideal for portable applications
short learning time
– keypresses reflect letter shape
fast
– once you have trained
BUT - social resistance, plus fatigue after
extended use
NEW –market for some wearables

 use numeric keys with
multiple presses
2 – a b c 6 - m n o
3 - d e f 7 - p q r s
4 - g h i 8 - t u v
5 - j k l 9 - w x y z
hello = 4433555[pause]555666
surprisingly fast!
 T9 predictive entry
 type as if single key for each letter
 use dictionary to ‘guess’ the right word
 hello = 43556 …
 but 26 -> menu ‘am’ or ‘an’

 Text can be input into the computer, using a
pen and a digitizing tablet
 natural interaction

 Technical problems:
 capturing all useful information - stroke path,
pressure, etc. in a natural manner
 segmenting joined up writing into individual letters
 interpreting individual letters
 coping with different styles of handwriting
 Used in PDAs, and tablet computers …
… leave the keyboard on the desk!

 Improving rapidly
 Most successful when:
 single user – initial training and learns peculiarities
 limited vocabulary systems
 Problems with
 external noise interfering
 imprecision of pronunciation
 large vocabularies
 different speakers

 for entering numbers quickly:
 calculator, PC keyboard
 for telephones
not the same!!
ATM like phone
4 5 6
7 8 9
* 0 #
1 2 3
4 5 6
1 2 3
0 . =
7 8 9
telephone calculator

mouse, touchpad
trackballs, joysticks etc.
touch screens, tablets
eyegaze, cursors

 Handheld pointing device
 very common
 easy to use
 Two characteristics
 planar movement
 buttons
(usually from 1 to 3 buttons on top, used for making a
selection, indicating an option, or to initiate drawing
etc.)

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 …
… an indirect manipulation device.
 device itself doesn’t obscure screen, is accurate and fast.
 hand-eye coordination problems for novice users

Two methods for detecting motion
 Mechanical
 Ball on underside of mouse turns as mouse is moved
 Rotates orthogonal potentiometers
 Can be used on almost any flat surface

Two methods for detecting motion
 Optical
 light emitting diode on underside of mouse
 may use special grid-like pad or just on desk
 less susceptible to dust and dirt
 detects fluctuating alterations in reflected light intensity to
calculate relative motion in (x, z) plane

 some experiments with the footmouse
 controlling mouse movement with feet …
 not very common :-)
 but foot controls are common elsewhere:
 car pedals
 sewing machine speed control
 organ and piano pedals

 small touch sensitive tablets
 ‘stroke’ to move mouse pointer
 used mainly in laptop computers
 good ‘acceleration’ settings important
 fast stroke
 lots of pixels per inch moved
 initial movement to the target
 slow stroke
 less pixels per inch
 for accurate positioning

Trackball
 ball is rotated inside static housing
 like an upside down mouse!
 relative motion moves cursor
 indirect device, fairly accurate
 separate buttons for picking
 very fast for gaming
 used in some portable and notebook computers.

Thumbwheels …
 for accurate CAD – two dials for X-Y cursor position
 for fast scrolling – single dial on mouse

Joystick
 indirect
pressure of stick = velocity of movement
 buttons for selection
on top or on front like a trigger
 often used for computer games
aircraft controls and 3D navigation

Keyboard nipple
 for laptop computers
 miniature joystick in the middle of the keyboard

 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 pointer
 good 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
 small pen-like pointer to draw directly on screen
 may use touch sensitive surface or magnetic detection
 used in PDA, tablets PCs and drawing tables

Light Pen
 now rarely used
 uses light from screen to detect location
BOTH …
 very direct and obvious to use
 but can obscure screen

 Mouse like-device with cross hairs
 used on special surface
- rather like stylus
 very accurate
- used for digitizing maps

 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

 Four keys (up, down, left, right) on keyboard.
 Very, very cheap, but slow.
 Useful for not much more than basic motion for text-
editing tasks.
 No standardised layout, but inverted “T”, most
common

 in phones, TV controls etc.
 cursor pads or mini-joysticks
 discrete left-right, up-down
 mainly for menu selection

bitmap screens (CRT & LCD)
large & situated displays
digital paper

 screen is vast number of coloured dots

 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 ratio
 ration between width and height
 4:3 for most screens, 16:9 for wide-screen TV
 Colour depth:
 how many different colours for each pixel?
 black/white or greys only
 256 from a pallete
 8 bits each for red/green/blue = millions of colours

Jaggies
 diagonal lines that have discontinuities in due to horizontal
raster scan process.
Anti-aliasing
 softens edges by using shades of line colour
 also used for text

 Stream of electrons emitted from electron gun,
focused and directed by magnetic fields, hit phosphor-
coated screen which glows
 used in TVs and computer monitors
electron gun
focussing and
deflection
electron beam
phosphor-
coated screen

 X-rays: largely absorbed by screen (but not at rear!)
 UV- and IR-radiation from phosphors: insignificant
levels
 Radio frequency emissions, plus ultrasound (~16kHz)
 Electrostatic field - leaks out through tube to user.
Intensity dependant on distance and humidity. Can
cause rashes.
 Electromagnetic fields (50Hz-0.5MHz). Create
induction currents in conductive materials, including
the human body. Two types of effects attributed to
this: visual system - high incidence of cataracts in
VDU operators, and concern over reproductive
disorders (miscarriages and birth defects).

 do not sit too close to the screen
 do not use very small fonts
 do not look at the screen for long periods
without a break
 do not place the screen directly in front of a
bright window
 work in well-lit surroundings
 Take extra care if pregnant.
but also posture, ergonomics, stress

 Smaller, lighter, and … no radiation problems.
 Found on PDAs, portables and notebooks,
… and increasingly on desktop and even for home TV
 also used in dedicated displays:
digital watches, mobile phones, HiFi controls

 How 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 colour
 N.B. light reflected not emitted => less eye strain

Random Scan (Directed-beam refresh, vector display)
 draw the lines to be displayed directly
 no jaggies
 lines need to be constantly redrawn
 rarely used except in special instruments
Direct view storage tube (DVST)
 Similar to random scan but persistent => no flicker
 Can be incrementally updated but not selectively erased
 Used in analogue storage oscilloscopes

 used for meetings, lectures, etc.
 technology
plasma – usually wide screen
video walls – lots of small screens together
projected – RGB lights or LCD projector
– hand/body obscures screen
– may be solved by 2 projectors +
– clever software
back-projected
– frosted glass + projector behind

 displays in ‘public’ places
 large or small
 very public or for small group
 display only
 for information relevant to location
 or interactive
 use stylus, touch sensitive screen
 in all cases … the location matters
 meaning of information or interaction is related to the
location

 small displays beside office doors
 handwritten notes left using stylus
 office owner reads notes using web interface
small displays
beside
office doors
handwritten
notes left
using stylus
office owner
reads notes
using web interface

positioning in 3D space
moving and grasping
seeing 3D (helmets and caves)

 cockpit and virtual controls
 steering wheels, knobs and dials … just like real!

 the 3D mouse
 six-degrees of movement: x, y, z + roll, pitch, yaw

pitch
yaw
roll

 data glove
 fibre optics used to detect finger position

 VR helmets
 detect head motion and possibly eye gaze

 whole body tracking
 accelerometers strapped to limbs or reflective dots
and video processing

 desktop VR
 ordinary screen, mouse or keyboard control
 perspective and motion give 3D effect
 seeing in 3D
 use stereoscopic vision
 VR helmets
 screen plus shuttered specs, etc.

 small TV screen for each eye
 slightly different angles
 3D effect

 time delay
 move head … lag … display moves
 conflict: head movement vs. eyes
 depth perception
 headset gives different stereo distance
 but all focused in same plane
 conflict: eye angle vs. focus
 conflicting cues => sickness
 helps motivate improvements in technology

 scenes projected on walls
 realistic environment
 hydraulic rams!
 real controls
 other people

special displays and gauges
sound, touch, feel, smell
physical controls
environmental and bio-sensing

 analogue representations:
 dials, gauges, lights, etc.

 digital displays:
 small LCD screens, LED lights, etc.

 head-up displays
 found in aircraft cockpits
 show most important controls
… depending on context

 beeps, bongs, clonks, whistles and whirrs
 used for error indications
 confirmation of actions e.g. keyclick

 touch and feeling important
 in games … vibration, force feedback
 in simulation … feel of surgical instruments
 called haptic devices
 texture, smell, taste
 current technology very limited

 for controlling menus
 feel small ‘bumps’ for each item
 makes it easier to select options by feel
 uses haptic technology from Immersion Corp.

 specialist controls needed …
 industrial controls, consumer products, etc.
large buttons
clear dials
tiny buttons
multi-function
control
easy-clean
smooth buttons

 sensors all around us
 car courtesy light – small switch on door
 ultrasound detectors – security, washbasins
 RFID security tags in shops
 temperature, weight, location
 … and even our own bodies …
 iris scanners, body temperature, heart rate,
galvanic skin response, blink rate

print technology
fonts, page description, WYSIWYG
scanning, OCR

 image made from small dots
 allows any character set or graphic to be
printed,
 critical features:
 resolution
 size and spacing of the dots
 measured in dots per inch (dpi)
 speed
 usually measured in pages per minute
 cost!!

 dot-matrix printers
 use inked ribbon (like a typewriter
 line of pins that can strike the ribbon, dotting the paper.
 typical resolution 80-120 dpi

 ink-jet and bubble-jet printers
 tiny blobs of ink sent from print head to paper
 typically 300 dpi or better .

 laser printer
 like photocopier: dots of electrostatic charge deposited on drum,
which picks up toner (black powder form of ink) rolled onto paper
which is then fixed with heat
 typically 600 dpi or better.

 shop tills
 dot matrix
 same print head used for several paper rolls
 may also print cheques

 thermal printers
 special heat-sensitive paper
 paper heated by pins makes a dot
 poor quality, but simple & low maintenance
 used in some fax machines

 Font – the particular style of text
Courier font
Helvetica font
Palatino font
Times Roman font
 §´  (special symbol)
 Size of a font measured in points (1 pt about 1/72”)
(vaguely) related to its height
This is ten point Helvetica
This is twelve point
This is fourteen point
This is eighteen point
and this is twenty-four point

Pitch
 fixed-pitch – every character has the same width
e.g. Courier
 variable-pitched – some characters wider
e.g. Times Roman – compare the ‘i’ and the “m”
Serif or Sans-serif
 sans-serif – square-ended strokes
e.g. Helvetica
 serif – with splayed ends (such as)
e.g. Times Roman or Palatino

 lowercase
 easy to read shape of words
 UPPERCASE
 better for individual letters and non-words
e.g. flight numbers: BA793 vs. ba793
 serif fonts
 helps your eye on long lines of printed text
 but sans serif often better on screen

 Pages very complex
 different fonts, bitmaps, lines, digitised photos, etc.
 Can convert it all into a bitmap and send to the
printer
… but often huge !
 Alternatively Use a page description language
 sends a description of the page can be sent,
 instructions for curves, lines, text in different styles, etc.
 like a programming language for printing!
 PostScript is the most common

 WYSIWYG
 what you see is what you get
 aim of word processing, etc.
 but …
 screen: 72 dpi, landscape image
 print: 600+ dpi, portrait
 can try to make them similar
but never quite the same
 so … need different designs, graphics etc, for
screen and print

 Take paper and convert it into a bitmap
 Shines light at paper and note intensity of reflection
 colour or greyscale
 Typical resolutions from 600–2400 dpi

 Two sorts of scanner
 flat-bed: paper placed on a glass plate, whole page converted into
bitmap
 hand-held: scanner passed over paper, digitising strip typically 3-
4” wide

Used in
 desktop publishing for incorporating
photographs and other images
 document storage and retrieval systems,
doing away with paper storage
+ special scanners for slides and photographic
negatives

 OCR converts bitmap back into text
 different fonts
 create problems for simple
“template matching”
algorithms
 more complex systems segment text,
decompose it into lines and arcs, and decipher
characters that way
 page format
 columns, pictures, headers and footers

 paper usually regarded as output
only
 can be input too – OCR, scanning,
etc.
 Xerox PaperWorks
 glyphs – small patterns of ///
 used to identify forms etc.
 used with scanner and fax to control applications
 more recently
 papers micro printed - like wattermarks
 identify which sheet and where you are
 special ‘pen’ can read locations
 know where they are writing

short term and long term
speed, capacity, compression
formats, access

 Random access memory (RAM)
 on silicon chips
 100 nano-second access time
 usually volatile (lose information if power turned off)
 data transferred at around 100 Mbytes/sec
 Some non-volatile RAM used to store basic set-up
information
 Typical desktop computers:
64 to 256 Mbytes RAM

 magnetic disks
 floppy disks store around 1.4 Mbytes
 hard disks typically 40 Gbytes to 100s of Gbytes
access time ~10ms, transfer rate 100kbytes/s

 optical disks
 use lasers to read and sometimes write
 more robust that magnetic media
 CD-ROM
- same technology as home audio, ~ 600 Gbytes
 DVD - for AV applications, or very large files

 PDAs
 often use RAM for their main memory
 Flash-Memory
 used in PDAs, cameras etc.
 silicon based but persistent
 plug-in USB devices for data transfer

 what do the numbers mean?
 some sizes (all uncompressed) …
 this book, text only ~ 320,000 words, 2Mb
 the Bible ~ 4.5 Mbytes
 scanned page ~ 128 Mbytes
 (11x8 inches, 1200 dpi, 8bit greyscale)
 digital photo ~ 10 Mbytes
 (2–4 mega pixels, 24 bit colour)
 video ~ 10 Mbytes per second
 (512x512, 12 bit colour, 25 frames per sec)

 Problem:
 running lots of programs + each program large
 not enough RAM
 Solution - Virtual memory :
 store some programs temporarily on disk
 makes RAM appear bigger
 But … swapping
 program on disk needs to run again
 copied from disk to RAM
 s l o w s t h i n g s d o w n

 reduce amount of storage required
 lossless
 recover exact text or image – e.g. GIF, ZIP
 look for commonalities:
 text: AAAAAAAAAABBBBBCCCCCCCC 10A5B8C
 video: compare successive frames and store change

 lossy
 recover something like original – e.g. JPEG, MP3
 exploit perception
 JPEG: lose rapid changes and some colour
 MP3: reduce accuracy of drowned out notes

 ASCII - 7-bit binary code for to each letter and
character

 RTF (rich text format)
- text plus formatting and layout information

 ASCII - 7-bit binary code for to each letter and
character
 UTF-8 - 8-bit encoding of 16 bit character set

 SGML (standardized generalised markup language)
- documents regarded as structured objects

 XML (extended markup language)
- simpler version of SGML for web applications

 Images:
 many storage formats :
(PostScript, GIFF, JPEG, TIFF, PICT, etc.)
 plus different compression techniques
(to reduce their storage requirements)
 Audio/Video
 again lots of formats :
(QuickTime, MPEG, WAV, etc.)
 compression even more important
 also ‘streaming’ formats for network delivery

 large information store
 long time to search => use index
 what you index -> what you can access
 simple index needs exact match
 forgiving systems:
 Xerox “do what I mean” (DWIM)
 SOUNDEX – McCloud ~ MacCleod
 access without structure …
 free text indexing (all the words in a document)
 needs lots of space!!

finite speed (but also Moore’s law)
limits of interaction
networked computing

 Designers tend to assume fast processors, and make
interfaces more and more complicated
 But problems occur, because processing cannot keep
up with all the tasks it needs to do
 cursor overshooting because system has buffered keypresses
 icon wars - user clicks on icon, nothing happens, clicks on another,
then system responds and windows fly everywhere
 Also problems if system is too fast - e.g. help screens
may scroll through text much too rapidly to be read

 computers get faster and faster!
 1965 …
 Gordon Moore, co-founder of Intel, noticed a
pattern
 processor speed doubles every 18 months
 PC … 1987: 1.5 Mhz, 2002: 1.5 GHz
 similar pattern for memory
 but doubles every 12 months!!
 hard disk … 1991: 20Mbyte : 2002: 30 Gbyte
 baby born today
 record all sound and vision
 by 70 all life’s memories stored in a grain of dust!

 implicit assumption … no delays
an infinitely fast machine
 what is good design for real machines?
 good example … the telephone :
 type keys too fast
 hear tones as numbers sent down the line
 actually an accident of implementation
 emulate in deisgn

Computation bound
 Computation takes ages, causing frustration for the user
Storage channel bound
 Bottleneck in transference of data from disk to memory
Graphics bound
 Common bottleneck: updating displays requires a lot of effort -
sometimes helped by adding a graphics co-processor optimised to
take on the burden
Network capacity
 Many computers networked - shared resources and files, access to
printers etc. - but interactive performance can be reduced by
slow network speed

Networks allow access to …
 large memory and processing
 other people (groupware, email)
 shared resources – esp. the web
Issues
 network delays – slow feedback
 conflicts - many people update data
 unpredictability

 history …
 1969: DARPANET US DoD, 4 sites
 1971: 23; 1984: 1000; 1989: 10000
 common language (protocols):
 TCP – Transmission Control protocol
 lower level, packets (like letters) between machines
 IP – Internet Protocol
 reliable channel (like phone call) between programs on
machines
 email, HTTP, all build on top of these

 interaction models
 translations between user and system
 ergonomics
 physical characteristics of interaction
 interaction styles
 the nature of user/system dialog
 context
 social, organizational, motivational

communication
user system
but is that all … ?
 see “language and action” in chapter 4 …

terms of interaction
Norman model
interaction framework

domain – the area of work under study
e.g. graphic design
goal – what you want to achieve
e.g. create a solid red triangle
task – how you go about doing it
– ultimately in terms of operations or actions
e.g. … select fill tool, click over triangle
Note …
 traditional interaction …
 use of terms differs a lot especially task/goal !!!

 Seven stages
 user establishes the goal
 formulates intention
 specifies actions at interface
 executes action
 perceives system state
 interprets system state
 evaluates system state with respect to goal
 Norman’s model concentrates on user’s view
of the interface

 user establishes the goal
 formulates intention
 specifies actions at interface
 executes action
 perceives system state
 interprets system state
 evaluates system state with respect to goal
system
evaluation
execution
goal

 executes action
system
evaluation
execution
goal

Some systems are harder to use than others
Gulf of Execution
user’s formulation of actions
≠ actions allowed by the system
Gulf of Evaluation
user’s expectation of changed system state
≠ actual presentation of this state

slip
understand system and goal
correct formulation of action
incorrect action
mistake
may not even have right goal!
Fixing things?
slip – better interface design
mistake – better understanding of system

extension of Norman…
their interaction framework has 4 parts
 user
 input
 system
 output
each has its own unique language
interaction  translation between languages
problems in interaction = problems in translation
S
core
U
task
O
output
I
input

user intentions
 translated into actions at the interface
 translated into alterations of system state
 reflected in the output display
 interpreted by the user
general framework for understanding
interaction
 not restricted to electronic computer systems
 identifies all major components involved in interaction
 allows comparative assessment of systems
 an abstraction

physical aspects of interfaces
industrial interfaces

 Study of the physical characteristics of
interaction
 Also known as human factors – but this can
also be used to mean much of HCI!
 Ergonomics good at defining standards and
guidelines for constraining the way we design
certain aspects of systems

 arrangement of controls and displays
e.g. controls grouped according to function or
frequency of use, or sequentially
 surrounding environment
e.g. seating arrangements adaptable to cope with all
sizes of user
 health issues
e.g. physical position, environmental conditions
(temperature, humidity), lighting, noise,
 use of colour
e.g. use of red for warning, green for okay,
awareness of colour-blindness etc.

Office interface vs. industrial interface?
Context matters!
office industrial
type of data textual numeric
rate of change slow fast
environment clean dirty
… the oil soaked mouse!

 industrial interface:
 traditional … dials and knobs
 now … screens and keypads
 glass interface
+ cheaper, more flexible,
multiple representations,
precise values
 not physically located,
loss of context,
complex interfaces
 may need both
Vessel B Temp
0 100 200
113
multiple representations
of same information

 office– direct manipulation
 user interacts
with artificial world
 industrial – indirect manipulation
 user interacts
with real world
through interface
 issues ..
 feedback
 delays
system
interface plant
immediate
feedback
instruments

dialogue … computer and
user
distinct styles of interaction

 command line interface
 menus
 natural language
 question/answer and query dialogue
 form-fills and spreadsheets
 WIMP
 point and click
 three–dimensional interfaces

 Way of expressing instructions to the
computer directly
 function keys, single characters, short abbreviations,
whole words, or a combination
 suitable for repetitive tasks
 better for expert users than novices
 offers direct access to system functionality
 command names/abbreviations should be
meaningful!
Typical example: the Unix system

 Set of options displayed on the screen
 Options visible
 less recall - easier to use
 rely on recognition so names should be meaningful
 Selection by:
 numbers, letters, arrow keys, mouse
 combination (e.g. mouse plus accelerators)
 Often options hierarchically grouped
 sensible grouping is needed
 Restricted form of full WIMP system

 Familiar to user
 speech recognition or typed natural language
 Problems
 vague
 ambiguous
 hard to do well!
 Solutions
 try to understand a subset
 pick on key words

 Question/answer interfaces
 user led through interaction via series of questions
 suitable for novice users but restricted functionality
 often used in information systems
 Query languages (e.g. SQL)
 used to retrieve information from database
 requires understanding of database structure and
language syntax, hence requires some expertise

 Primarily for data entry or data retrieval
 Screen like paper form.
 Data put in relevant place
 Requires
 good design
 obvious correction
facilities

 first spreadsheet VISICALC, followed by
Lotus 1-2-3
MS Excel most common today
 sophisticated variation of form-filling.
 grid of cells contain a value or a formula
 formula can involve values of other cells
e.g. sum of all cells in this column
 user can enter and alter data spreadsheet
maintains consistency

Windows
Icons
Menus
Pointers
… or windows, icons, mice, and pull-down menus!
 default style for majority of interactive
computer systems, especially PCs and
desktop machines

 used in ..
 multimedia
 web browsers
 hypertext
 just click something!
 icons, text links or location on map
 minimal typing

 virtual reality
 ‘ordinary’ window systems
 highlighting
 visual affordance
 indiscriminate use
just confusing!
 3D workspaces
 use for extra virtual space
 light and occlusion give depth
 distance effects
flat buttons …
… or sculptured
click me!

windows, icons, menus, pointers
+++
buttons, toolbars,
palettes, dialog boxes

 Areas of the screen that behave as if they
were independent
 can contain text or graphics
 can be moved or resized
 can overlap and obscure each other, or can be laid
out next to one another (tiled)
 scrollbars
 allow the user to move the contents of the window up
and down or from side to side
 title bars
 describe the name of the window

 small picture or image
 represents some object in the interface
 often a window or action
 windows can be closed down (iconised)
 small representation ﬁ many accessible
windows
 icons can be many and various
 highly stylized
 realistic representations.

 important component
 WIMP style relies on pointing and selecting things
 uses mouse, trackpad, joystick, trackball,
cursor keys or keyboard shortcuts
 wide variety of graphical images

 Choice of operations or services offered on the
screen
 Required option selected with pointer
problem – take a lot of screen space
solution – pop-up: menu appears when needed
File Edit Options
Typewriter
Screen
Times
Font

 Menu Bar at top of screen (normally), menu
drags down
 pull-down menu - mouse hold and drag down menu
 drop-down menu - mouse click reveals menu
 fall-down menus - mouse just moves over bar!
 Contextual menu appears where you are
 pop-up menus - actions for selected object
 pie menus - arranged in a circle
 easier to select item (larger target area)
 quicker (same distance to any option)
… but not widely used!

 Cascading menus
 hierarchical menu structure
 menu selection opens new menu
 and so in ad infinitum
 Keyboard accelerators
 key combinations - same effect as menu item
 two kinds
 active when menu open – usually first letter
 active when menu closed – usually Ctrl + letter
usually different !!!

 which kind to use
 what to include in menus at all
 words to use (action or description)
 how to group items
 choice of keyboard accelerators

 individual and isolated regions within a
display that can be selected to invoke an
action
 Special kinds
 radio buttons
– set of mutually exclusive choices
 check boxes
– set of non-exclusive choices

 long lines of icons …
… but what do they do?
 fast access to common actions
 often customizable:
 choose which toolbars to see
 choose what options are on it

 Problem
menu not there when you want it
 Solution
palettes – little windows of actions
 shown/hidden via menu option
e.g. available shapes in drawing package
tear-off and pin-up menus
 menu ‘tears off’ to become palette

 information windows that pop up to inform
of an important event or request
information.
e.g: when saving a file, a dialogue box is
displayed to allow the user to specify the
filename and location. Once the file is saved,
the box disappears.

easy to focus on look
what about feel?

 rapidly improving …
… but still inaccurate
 how to have robust dialogue?
… interaction of course!
e.g. airline reservation:
reliable “yes” and “no”
+ system reflects back its understanding
“you want a ticket from New York to Boston?”

 WIMP systems have the same elements:
windows, icons, menus, pointers, buttons, etc.
 but different window systems
… behave differently
e.g. MacOS vs Windows menus
appearance + behaviour = look and feel

 who has the initiative?
old question–answer– computer
WIMP interface – user
 WIMP exceptions …
pre-emptive parts of the interface
 modal dialog boxes
 come and won’t go away!
 good for errors, essential steps
 but use with care

can’t always avoid errors …
… but we can put them right
make it easy to detect errors
… then the user can repair them
hello, this is the Go Faster booking system
what would you like?
(user) I want to fly from New York to London
you want a ticket from New York to Boston
(user) no
sorry, please confirm one at a time
do you want to fly from New York
(user) yes
… … …

Interaction affected by social and organizational
context
 other people
 desire to impress, competition, fear of failure
 motivation
 fear, allegiance, ambition, self-satisfaction
 inadequate systems
 cause frustration and lack of motivation

designing experience
physical engagement
managing value

 home, entertainment, shopping
 not enough that people can use a system
 they must want to use it!
 psychology of experience
 flow (Csikszentimihalyi)
 balance between anxiety and boredom
 education
 zone of proximal development
 things you can just do with help
 wider ...
 literary analysis, film studies, drama

 real crackers
 cheap and cheerful!
 bad joke, plastic toy, paper hat
 pull and bang

 virtual crackers
 cheap and cheerful
 bad joke, web toy, cut-out mask
 click and bang

sender
fill in web form
To: wxv
From: ..
receive email recipient
closed
cracker page
open
message
recipient clicks
cracker opens ...
very slowly
joke
links
open
cracker page
web toy
mask
sender
watches
progress

real cracker virtual cracker
Surface elements
design cheap and cheerful simple page/graphics
play plastic toy and joke web toy and joke
dressing up paper hat mask to cut out
Experienced effects
shared offered to another sent by email message
co-experience pulled together sender can't see content
until opened by recipient
excitement cultural connotations recruited expectation
hiddenness contents inside first page - no contents
suspense pulling cracker slow ... page change
surprise bang (when it works) WAV file (when it works)

 many constraints:
 ergonomic – minimum button size
 physical – high-voltage switches are big
 legal and safety – high cooker controls
 context and environment – easy to clean
 aesthetic – must look good
 economic – … and not cost too much!

constraints are contradictory … need trade-offs
within categories:
e.g. safety – cooker controls
front panel – safer for adult
rear panel – safer for child
between categories
e.g. ergonomics vs. physical – MiniDisc remote
ergonomics – controls need to be bigger
physical – no room!
solution – multifunction controls & reduced functionality

 do external physical aspects reflect logical
effect?
 related to affordance (chap 5)
logical state revealed in physical state?
e.g. on/off buttons
inverse actions inverse effects?
e.g. arrow buttons, twist controls

 yes/no buttons
 well sort of
 ‘joystick’
 also left side control

 one-shot buttons
 joystick
 some sliders
good – large selection sets
bad – hidden state

series of spring-back controls
each cycle through some options
–natural inverse back/forward
twist for track movement
pull and twist for volume
– spring back
– natural inverse for twist

controls:
logical relationship
~ spatial grouping

state evident in
mechanical buttons rotary knobs reveal internal state
and can be controlled by both user
and machine

people use something
ONLY IF
it has perceived value
AND
value exceeds cost
BUT NOTE
 exceptions (e.g. habit)
 value NOT necessarily personal gain or money

value
 helps me get my work done
 fun
 good for others
cost
 download time
 money £, $, €
 learning effort

 in economics Net Present Value:
 discount by (1+rate)years to wait
 in life people heavily discount
 future value and future cost
 hence resistance to learning
 need low barriers
and high perceived present value

 value for people who have the book
helps you to look up things
 chapter and page number
 value for those who don’t …
sort of online mini-encyclopaedia
 full paragraph of context
… but also says “buy me”!!
… but also says “buy me”!!

 coercion
 tell people what to do!
 value = keep your job
 enculturation
 explain corporate values
 establish support (e.g share options)
 emergence
 design process so that
individuals value  organisational value

 Alan Dix- Janet Finlay Gregory D.
Abowd- Russel Beale- Human –
Computer Interaction, Pearson
Education- 3 rd Edition- 2004.
 John M.Caroll, Human – Computer
Interaction in the Millennium,
Pearson Education- 3rd Edition-
2000.
8/22/2011

1. State law of size constancy.
2. State Fitts law.
3. What is saccade?
4. List the three types of sensory receptors
in skin.
5. What is recency effect?
6. Mention the two types of long term
memory.
7. What is total time hypothesis?
8. What is distribution of practice effect?
8/22/2011

9. What is Retroactive interference?
10. What is proactive inhibition?
11. What is deductive reasoning?
12. What is inductive reasoning?
13. Differentiate track ball and mouse.
14. Draw the various cursor key layouts.
15. What is antialiasing?
16. What is the use of virtual reality helmets?
8/22/2011

17. List the factors that can limit the speed of
an interactive system.
18. Define ergonomics.
19. List the factors in the physical
environment that directly affect the
quality of the interaction and the user’s
performance.
20. What is a palette?
8/22/2011

18 cse366t human computer interaction - hci - unit i

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18 cse366t human computer interaction - hci - unit i