Chapter 1The Human
Department of Computing & Information Systems, SUSL
Human Computer Interaction
Dissect HCI definition
Human, Users, single, group working together User(s) tries to complete a task.
Computer, Technology, not just Desktop computer Systems:
Large-scale computers, Process control, Embedded systems.
Interaction, Communication, direct/indirect Dialogue + feedback/batch Task oriented
The human
Information through i/o channels vision, hearing, touch, movement
Information stored in memory sensory, short-term, long-term
Information processed and applied reasoning, problem solving, skill, errors, learn
Emotion influences human capabilities Each person is different
Vision
Two stages in vision
• physical reception of stimulus from the outside world
• processing and interpretation of stimulus
visual processing This ability to interpret and exploit our
expectations can be used to resolve ambiguity.
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
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.(we can
pick
out our name spoken across a crowded noisy room)
Hearing cont..
Just as vision begins with light, hearing begins with vibrations in the air or sound waves. The ear receives these vibrations and transmits them, through various stages, to the auditory nerves.
Exercise: Suggest ideas for an interface which uses the properties of sound effectively.
Status information – continuous background sounds can be used to convey status information. For example, monitoring the progress of a process (without the need for visual attention).
Confirmation – a sound associated with an action to confirm that the action has been carried out. For example, associating a sound with deleting a file.
Navigation – using changing sound to indicate where the user is in a system. For example, what about sound to support navigation in hypertext?
Touch (haptic perception)
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.
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.
Memory
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.
Design Focus
Sensory Memory
acts as a buffer for stimuli received through the five senses of sight, hearing, smell, taste and touch
Constantly overwritten Eg:
Short –term(working) Memory
acts as a “scratch-pad” for temporary recall of the information. the ability to remember and process information at the same
time. holds a small amount of information (around 7 items or even less) in
mind in an active, readily-available state for a short period of time (from 10 to 15 seconds, or sometimes up to a minute)
Design Focus..
Long -term Memory
- rehearsal information moves from STM to LTM
- store factual information, experiential knowledge.- huge or unlimited capacity- slow access ~ 1/10 second- forgetting occurs more slowly .- Information is placed there from working memory through
rehearsal.- decay ( information is lost gradually but very slowly)
- Two types
episodic – serial memory of events
semantic – structured memory of facts, concepts, skills
Long-term memory may store information in a semantic network…
Thinking: Reasoning and problem solving
Reasoning is the process by which we use the knowledge we have to draw conclusions or infer something new about the domain of interest.
This is perhaps the area which is most complex and which separates humans from other information-processing systems, both artificial and natural.
Deductive Reasoning
Deduction: derive logically necessary conclusion from given premises.
e.g. All men are mortal. Harry is a man. Therefore, Harry is mortal.
Logical conclusion not necessarily true:e.g. All bald men are grandfathers.
Harry is bald. Therefore, Harry is a grandfather
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!
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Abductive reasoning
reasoning from event to cause (this is the method that we use to derive
explanations for the events we observe) e.g. Sam drives fast when drunk. If I see Sam driving fast, assume drunk.
Unreliable: can lead to false explanations
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Problem solving
Problem solving is the process of finding a solution to an unfamiliar task, using the knowledge we have
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
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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
Emotions
Emotions highly affect human’s reasoning, problem solving ,performance, errors etc..
Eg : Positive emotions enable us to think more creatively, to solve complex problems,
whereas negative emotion pushes us into narrow thinking
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Individual Differences
Users, are not all the same.
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?
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