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?