Chapter 1 The 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!

Abductive reasoning 20  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

Problem solving 21 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

Errors and mental models 22 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

Individual Differences 24 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?