On Human Computer Interaction, HCI. Dr. Saif al Zahir Electrical and Computer Engineering Department UBC

Transcription

1 On Human Computer Interaction, HCI Dr. Saif al Zahir Electrical and Computer Engineering Department UBC

2 Human Computer Interaction HCI HCI is the study of people, computer technology, and the ways these influence each other. We study HCI to determine how we can make this computer technology more usable for people. HCI is a multidisciplinary practice: Engineering Computer Science Sociology Cognitive psychology Ergonomics

3 Why HCI?.. Numerous Applications.. E-commerce Computer-aided surgery (medical applications) Remote learning (distance education) Computer aided Planning, Manufacturing,... Tourism GIS you name it...

4 H-C strengths and weaknesses Human Powerful pattern recognition powerful selective attention capacity to learn infinite-capacity LTM rich multikeyed LTM Computer High-capacity memory permanent memory very fast processing error-free processing reliable memory access

5 H-C strengths and weaknesses Low capacity working memory fast decaying working memory slow processing error prone processing unreliable access to LTM Simple template matching limited learning capacity limited capacity LTM limited data integration

6 HCI Objectives Interaction between a human user and a computer system via the medium of an interface. - usability criteria. HCI makes use of new and novel techniques and technologies to make working with computers easier and more productive. HCI aims to achieve more usable systems and more satisfied users. Pragmatics: legislative, financial and usability constraints as well as safety-critical.

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8 Door

9 Good User Interface

10 What is an Interface?.. Possible Definitions A collection of input and output devices Surface forming common boundary of two systems A place for conversation Place where the interaction occur between two systems All the information channels that allow the user and the object to communicate

11 Why High quality UI??.. Whether a user enjoy or despise a system Whether a system succeeds or fails in a market Example 1: Nuclear power plant monitoring system. A poor UI can contribute to and even cause accident of catastrophic nature Example 2: Air Traffic Control

12 Styles of UI 1. What you see is what you get (WYSIWYG) 2. Direct Manipulation the objects, attributes, or relations that can be operated on are represented visually. Use a mouse to invoke. 3. Iconic A pictorial representation of an object, an action, a property, or some other concept recognition, remembering, and discrimination

13 Main Objectives in User Interface Design 1. Increase the speed of learning measure: how long a new user takes to achieve certain level of proficiency. 2. Speed of Use measure : how long an experienced user require to perform certain task with a system 3. Reduction of errors measure: the number of user errors per interaction 4. Attractive to buyers and users target : computer naive users

14 UI as a system 1. Interaction devices (input / output) 2. Interaction techniques: ways to use input devices to enter information into the computer 3. Interaction tasks classify the fundamental types of information entered with interaction techniques - position -text - select - quantify

15 UI Design Methods There is no cookbook approach that ensure good interface design Why?? 1. Some of the design principles are based on expert s experience and logical deduction from related fields such as cognitive psychology, rather than hard data 2. For any given design problem, guidelines will usually come in direct conflict with each other, and there are no algorithms for making the trade-offs UI design is a matter of Compromise & Trade-off

16 Examples on conflicting requirements Want : powerful functionality But simple and clear interface Want: ease of use But also ease of learning Want: consistency across all aspects of the interface But optimize operation Want intelligent and sophisticated interface But good performance and low cost. Results : We need methods to solve these conflicting requirements

17 Correspondence

18 Graphic Interface

19 Theories of Human Behavior Psychological Sociological Anthropological Develop a Model to help us understand and predict human behavior Provide simple examples of predictions

20 Theories of Human Social Behavior 1. Explanatory theories 2. Empirical theories 3. Dynamic Models Study them and the way they support design

21 1. Explanatory theories Explains observed human behavior explain things we see people doing help in evaluation (i.e., newly installed sys.) why system impact is different from expected study users and analyzing their needs Example 1: Users using keyboard shortcuts more than expected cause of high latencies in menu display Example 2: Air traffic controllers failing to trust a system because it undermined their team-oriented working style.

22 2. Empirical Laws Empirical Laws offer simple quantitative prediction of human performance Example : Hick s Law (1952) The time T taken to choose between a number of alternative targets is a function of the number of the targets n, and is related logarithmically : T = k log ( n + 1) Where k is a constant

23 2. Empirical Laws Examples: the correlation between size of menu and the time to make a selection cycle times of the human brain the time taken to move the mouse to a target of a given size from a given distance away.

24 3. Dynamic Models Models that predict how a whole sequence of actions (steps) will be performed models which predict the sequence of actions a user will take model which predict the level of performance if a given sequence of actions is taken by the user

25 3. Dynamic Models Predict the speed with which the user can perform an activity example : keyboard interaction speed simple dynamic model to predict the speed of operation of keyboard-based user-interface Cycle times (can use this for the zigzag example) perceptual msec Average: 100 ms cognitive msec Average: 70 ms motor msec Average: 70 ms

26 3. Dynamic Models Fitts Law This Law tells us how long it will take a user to hit a target of certain diameter, W, with a pointing device that is a certain distance, A, away. It uses the information processing model. T = K log( 2 A / W )

27 Design of the User Interface Factors that must be considered 1. How menus are to be organized. 2. How the graphics package is to respond to the input and errors. 3. How the output display is to be organized 4. How the package to be documented and explained to the user

28 Components of the User Interface User Model Command Language Menu Format Feedback Methods Output Format.

29 1. User Model Provides definition of the concepts involved in the graphics package Helps the user to understand how the package operates in terms of application concepts Explain to the user what type of objects can be displayed and how they can be manipulated.

30 2. Command Language Must be as natural as possible for the user to learn minimize memorization each operation in a command language should be structured so as to be easy to understand and remember no abbreviation (minimum). Ex. Select - Object is easier to remember than SO small set of operation

31 3. Menu Design Most computer graphics make use of menus Cut down on the amount of memorization Preventing users from selecting invalid options menus can easily be changed to accommodate different applications, whereas function keys must be reprogrammed and relabled if they are changed Menus with fewer options are more effective Placed on one side of the screen Can develop multilevel structure menu limit the number of levels

32 4. feedback The system must have a continual interactive dialogue and inform the user what the system is doing at each step. Special symbol can be designed for different types of feedback Example : a blinking at work sign to tell the user that the system is still processing Example : Mis-spelled words in Window 9x are underlined with red color

33 5. Output Format Information presented to the user 1. Output pictures 2. Menus 3. Messages 4. Other forms of dialogue generated by the system

34 5. Output Format-2 Format Design to achieve greatest effectiveness 1. Icon and symbol shapes Simple and clear picture of the object or operation they represent 2. Screen Layout main components (a) main area (b) Menu area (c) Display prompts and feedback area.

35 5. Output Format-3 1. Flexibility must be given to the user 2. Introduce overlapping window areas 3. Zoom capability to expand or enlarge portion of a picture Work Area Prompts and feedback messages Menu

36 wisdom No matter how cool is your interface, less of it would be better. Alan Cooper, Father of Visual Basic We think logically not visually We base our design on our own knowledge rather than the users We make our programs take control We think in generalities, not specific

37 Human Information Processing System, HIPS Basic Components Memory (short-term and long-term) Input (eyes, ears, touch) Output (hands, voice, eyes) Processes (executive control unit, pattern recognition, knowledge and skills

38 Human Memory Short Term Memory, STM memory buffer with low capacity (7 ± 2 units) a brief trace duration (few seconds) Can help STM by Grouping stored information. Example: remembering vs Long Term Memory, LTM powerful storage permanent in duration information is stored in a very rich, complex, and dynamic structure (this requires reorganization constantly) retrieval processes are slow, unreliable, and difficult. (need more concentration to get information from LTM)

39 Human Information Processor Model Based on classic information processing model (a) set of memories and processors (b) three interacting subsystems: - perceptual - motor and - cognitive Principle of operation is the recognize-act cycle (c) properties that can be measured include: - processor cycle time - memory decay rate - memory capacity

40 Types of Theory in HCI Exploratory theories To explain observed human behavior can provide useful insights in design lack predictive power Empirical laws Simple quantitative predictions of human performance (example: Fitts law for the time taken to point to a target of a particular size).

41 Usability The term usability has become central to the field of HCI. It can be defined very generally as: Making systems safe, easy to learn and easy to use. A more formal definition is: The degree to which specific users can achieve specific goals in a particular environment with efficiency, effectiveness, satisfaction.

42 Theory of Action Action is a series of progressive mental steps, resulting in a physical action. Outcome of a physical action at the interface is mentally evaluated in a series of steps. Stage 1- Mental Steps before physical action deciding planning translating executing Stage 2 - Corresponding steps after action perceiving recognizing interpreting evaluating

43 Task Performance 7-Steps for Task Performance Execution Establishing the Goals Forming the intention Specifying the action (Planned action sequence corresponding to intention) Executing the action Evaluation Perceiving the system state Interpreting the system state (trying to make sense of it as in expectation) Evaluating the outcome with respect to the goal and intention

44 Gulf of Execution and Gulf of Evaluation Gulf of Execution Is the difference between the intention of the person and the perceived allowable action. Gulf of Evaluation Is the difference between the cisible state of the system and the correct interpretation of the state of the system.

45 Uses of GOMS Goals, Operations, Methods, and Selection Rules Used in: comparing alternative systems. describing how same task is performed in different systems (keystroke method can be used to work out which system is fastest. developing training materials. describing the most efficient way to perform tasks. evaluating the consistency and completeness of a design. Advantages: cheap and relatively quick to carry out. systems that don t yet exist, but which are being designed, can be evaluated.

46 Methodology Phases Scoping Functional Specifications Design Development Testing/Implementation

47 Scoping Adding Human factors to Software Development Application Project Team User Interface Group Business Definition Scoping Project Plan Business Requirement Analysis User Profile HW & SW Definition

48 Developments in the Interface 50s - Interface with engineers at the hardware (level 1). interface was at the hardware level. 60/70s- interface with high level programming (level 2). software engineering and management. 70/90s Interface at the terminal (level 3). interactivity, command languages. 80s - Interface at interaction dialogue (level 4). GUIs, colour, sound, 3-D, animation. 90s - Interface at the work setting (level 5). networked systems, VR.