Ch1_TheHuman.pdf

Imam Mohammad Ibn Saud Islamic University College of Computer and Information Sciences Computer Science Department CS351: Human Computer Interaction Chapter 1: The Human Understanding users Facets of Inter...

Imam Mohammad Ibn Saud Islamic University College of Computer and Information Sciences Computer Science Department CS351: Human Computer Interaction Chapter 1: The Human Understanding users Facets of Interaction Prepared by Dr. Abeer Al-Nafjan  Human Computer Interaction Foundations Ch1: Human Ch2: Computer Ch3: Interaction the end-user of a the machine the program the user tells the computer program or others in the runs on what they want the organization computer communicates with results Input and output channels (Vision, Hearing, Touch, Movement) Memory (Sensory, short-term, Long-term) Understanding Thinking (Reasoning, Problem solving, skill acquisition, Error) users Emotion Individual differences Psychology and the design of interactive systems (Guideline, Facets of Models to support design, Techniques for evaluation) Interaction 2 What is HCI? HCI stands for Human Computer Interaction. It studies the design, implementation, and evaluation of interactive computing systems for human use. Its focus is on the ‘interface’ between the human and computer. The goal of HCI is to improve interaction between the human and computer by improving the usability of computer interfaces 3 What is HCI? The phrase Human-Computer interaction starts with ‘human’; The user whom computers are designed to assist. The user’s requirements should be the first priority when designing any computer system. This is constrained by users’ capabilities and limitations. 4 The Human Information is received and responses given via a number of input and output channels: ◼ Visual channel ◼ Auditory channel ◼ Haptic channel ◼ Movement Information is stored in memory: ◼ Sensory memory ◼ Short-term (working) memory ◼ long-term memory Information is processed applied: ◼ Reasoning ◼ Problem solving ◼ Skill acquisition ◼ Error 5 Interacting with computers A person’s interaction with the outside world occurs through information being received and sent: User’s input Computer’s output User’s output Computer’s input 6 Input–Output Channels Users’ input from the computer is via senses ▪ Vision ▪ Hearing ▪ Touch ▪ Taste and smell Users’ output to the computer is via effects ▪ Limbs ▪ Fingers ▪ Eyes ▪ Head ▪ Vocal system 7 Vision Two stages in vision 8 Vision Physical reception of stimulus (light) 9 Visual perception Perceiving size and depth ▪ Visual Angle ▪ Depth ▪ Familiarity Brightness ▪ luminance which is the amount of light emitted by an object ▪ Contrast: it is a function of the luminance of an object and the luminance of its background. Color ▪ Hue: the wavelength of the light ▪ Intensity: the brightness of the color ▪ Saturation: the amount of whiteness in the color 10 Capabilities and limitations of visual processing Using context to resolve ambiguity 11 Reading Adults read approximately 250 words a minute The speed at which text can be read is a measure of its legibility Word shape is important to recognition Reading from a computer screen is slower than a book Experiments have shown that standard font sizes of 9 to 12 points are equally legible Negative contrast (dark characters on a light screen) improves reading from computer screen 12 Which is easiest to read and why? What is the time? What is the time? What is the time? What is the time? What is the time? Hearing Hearing provides information about the environment ▪ distances, directions, objects, etc. The auditory system filters sounds which allows us to ignore background noise and concentrate on important information A person is able to attend to sounds over background noise ▪ Example: in a party you can hear your name being called or hear someone talking to you, while ignoring the background noise ▪ Interface examples: attention, status information, confirmation 14 Touch Touch provides important feedback about the environment. For someone that is visually impaired, touch is a key sense. Some areas in the human body are more sensitive than others. 15 Movement In HCI, a simple action such as hitting a button in response to a questions involves a number of processing stages 1. The stimulus (the question) is received through the sensory receptors and transmitted to the brain 2. The question is proceed in the brain 3. A valid response is generated 4. The brain tells the appropriate muscles to respond 16 Movement The time takes to reposed to a stimulus is called response time. Response time = reaction time + movement time Movement time is dependent on age, fitness, etc. 17 Movement Reaction time is dependent on stimulus type A combined signal results in a quicker response Speed and accuracy of movement are important considerations in the design of interactive systems. Does fast reaction reduce accuracy? For unskilled users, yes, but not for skilled users 18 Movement Fitts’ law describes the time taken to hit a screen target Movement time = a + b log2(Distance/Target size + 1) a and b are constants determined empirically How does Fitts’ law affect the types of targets to design? Pie-chart menu is preferable to list since all options are equidistance. A trade-off is increased use of screen estate. List menu Pie-chart menu 19 Human Memory Maintenance rehearsal Attention Encoding Sensory Short-term Long-term memory memory memory Sensory input Retrieval Unattended Unrehearsed Some information information is lost information is lost may be lost over time 20 Sensory Memory (SM) Sensory memory is the shortest-term element of memory. It acts as a kind of buffer for stimuli received through the five senses of sight, hearing, smell, taste and touch. Smell may be more closely linked to memory than the other senses. Information passed from sensory memory to short-term memory by attention, thereby filtering the stimuli to those of interest. 21 Short-term Memory (STM) Short-term memory has limited capacity: 7+-2 chunks Data grouped into chunks or with a meaning are easier for STM to remember and understand 22 Long-term memory (LTM) It is the main repository for all our knowledge. Rehearsal: information moves from STM to LTM Information can be retrieve via recall and recognition. Structure, meaning, and familiarity are important for remembering. ▪ Words of objects are easier to remember than those of concepts ▪ Sentences are easier to remember than words ▪ Using familiar icons makes it easier to understand and remember the function of a button in an interface 23 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. ▪ Deductive Reasoning: derive logically necessary conclusion from given premises. ▪ Inductive Reasoning: generalize from cases seen to cases unseen ▪ Abductive Reasoning: reasoning from event to cause If it is Friday All elephants we have If I see Sam driving then she will go seen have trunks fast, assume he is to work therefore all elephants have trunks. late. Deductive Reasoning Inductive Reasoning Abductive Reasoning 24 Thinking: Reasoning And Problem Solving Reasoning is a means of inferring new information from what is already known. Problem solving is the process of finding a solution to an unfamiliar task, using the knowledge we have. 25 Errors and Mental Models Humans make mistakes (fact). Some are trivial, others may be more serious. 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 (i.e drive home) Mistakes ▪ Wrong intention (may not have right goal) ▪ Cause: incorrect understanding ▪ Ex: German Hotel Elevator 26 Emotion Emotion influences human capabilities. The biological response to physical stimuli is called affect Emotion is an affective state induced by a specific stimulus. 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 27 Individual differences Users share common capabilities but are individuals with differences, which should not be ignored. Differences ▪ Long term: gender, physical and intellectual abilities ▪ Short term: effect of stress or fatigue ▪ Changing: age 28 Psychology & the design of interactive systems How can we apply what we have learned to designing interactive systems? Straightforward conclusions; i.e. since recognition is easier than recall -> allow users to select commands from a set (such as a menu) rather than input them directly. Majority of cases; application is not so obvious or simple and maybe dangerous- context is crucial. Principles and results from research in psychology have been distilled into guidelines for design, models to support design, and techniques for evaluating design. 29 HCI and the Human Vision ▪ Users concentrating on the centre of the screen can not see help or alerts that appear on the bottom of the screen. Use flashing! ▪ With Reading; Color, font, and size of text are important Touch ▪ Braille printers and pads ▪ Virtual shopping, ‘handling goods’ Hearing ▪ Sound amplitude, frequency, and tone ▪ Selecting the right alert for users with special needs Movement ▪ Button size ▪ Menu size and distance 30