This document provides an overview of key concepts in human-computer interaction (HCI). It discusses three main areas: 1) definitions of HCI and why it is important, focusing on usability and accessibility, 2) aspects of human cognition relevant to design such as perception, memory, problem solving, and individual differences, and 3) direct applications of psychology principles to interface design. The goal is to understand users and incorporate findings from cognitive psychology into interactive systems.
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Hci lecture 01_00
1. Human Computer Interaction
Dr. Sajjad Ahmed Nadeem
Department of Computer Science & IT
University of Azad Jammu & Kashmir
Muzaffarabad
Fall-2012
2. Text Books/ Reading Material
Alan Dix, Janet Finlay, Gregory D. Abowd
and Russell Beale. Human-Computer
Interaction (3rd edition). Prentice Hall, 2004.
Lecture Slides.
Every thing discussed in class is part of the
course material.
3. Tentative Marks Distribution
150
60 15 75
midterm Q+A Terminal
Min Max
Number of Quizzes 2 ……..
Number of Assignments 2 ……...
Number of Lab Assignments 3 ……...
4. What is HCI? (1)
The study of how people interact with computers and
to what extent computers are or are not developed for
successful interaction with human beings.
“Human-computer interaction is a discipline concerned
with the design, evaluation and implementation of
interactive computing systems for human use and
with the study of major phenomena surrounding them”
(ACM SIGCHI definition of HCI).
5. What is HCI? (2)
“the study of the interaction between people, computers
and tasks” (Johnson)
“a very difficult business. It combines two awkward
disciplines: psychology (Cognitive psychology) and
computer science” (Thimbleby)
Cognitive psychology is a subdiscipline of psychology
exploring internal mental processes.
It is the study of how people perceive, remember, think, speak,
and solve problems
6. Why is HCI Important?
HCI can assist in building products/systems that are
Useful, accomplish what’s required
Usable, do it easily and naturally
Used, make people want to use them
Increasing participation
Ensuring interfaces and systems are accessible.
International Directives and Standards (EC Directive
90/270/EEC; ISO 9241) place requirements on systems
in terms of usability
Safety and Security
Remember robots…..
9. The Human [1]
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
10. The Human [2]
In 1983, Card, Moran and Newell described the
Model Human Processor, comprising three
subsystems:
the perceptual system, handling sensory stimulus
from the outside world,
the motor system, which controls actions,
the cognitive system, which provides the processing
needed to connect the two.
The model also includes a number of principles
of operation which dictate the behavior of the
systems under certain conditions.
11. Cognitive Psychology
a subdiscipline of psychology exploring
internal mental processes.
is the study of how people perceive,
remember, think, speak, and solve problems.
is the branch of psychology that studies
mental processes including how people think,
perceive, remember and learn.
12. INPUT–OUTPUT CHANNELS
A person’s interaction with the outside world
occurs through information being received
and sent: input and output.
There are five major senses:
Sight
Hearing
Touch
Taste
Smell.
13. Vision
Two stages in vision
physical reception of stimulus
processing and interpretation of stimulus
14. Vision
The cornea and lens
at the front of the eye
focus the light into a
sharp image on the
back of the eye, the
retina.
The retina is light
sensitive and contains
two types of
photoreceptor: rods
and cones.
15. The Eye - physical reception
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
16. Interpreting the signal (1)
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
17. Interpreting the signal (2)
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
18. Interpreting the signal (3)
The visual system compensates for:
movement
changes in luminance.
Context is used to resolve ambiguity
Optical illusions sometimes occur due to over
compensation
20. Reading
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
21. Hearing
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
22. Hearing (cont)
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.
23. Touch
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.
24. Movement
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.
25. Movement (cont)
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
26. Memory
There are three types of memory function:
Sensory memories
Short-term memory or working memory
Long-term memory
30. Long-term memory (LTM)
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
31. Long-term memory (cont.)
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
33. Models of LTM - Frames
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
34. 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
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
35. Models of LTM - Production rules
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
36. 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 by spreading learning over time
structure, meaning and familiarity
information easier to remember
37. 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
38. LTM - retrieval
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
40. Deductive 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 dry
It is raining
Therefore the ground is dry
41. Deduction (cont.)
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
42. Inductive Reasoning
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.
43. 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
44. 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
45. Problem solving
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
46. Problem solving (cont.)
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
47. Problem solving (cont.)
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
48. Errors and mental models
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
49. 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 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
50. Emotion (cont.)
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)
51. Emotion (cont.)
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
52. Individual differences
long term
– sex, physical and intellectual abilities
short term
– effect of stress or fatigue
changing
– age
Ask yourself:
will design decision exclude section of user population?
53. Psychology and the Design of
Interactive System
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)