on human computer interaction, hci - ubc ecesaifz/eece478/course/hci-slides.pdf · 2001-05-07 ·...
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On Human Computer Interaction, HCI
Dr. Saif al ZahirElectrical and Computer Engineering Department
UBC
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
Why HCI ?..
Numerous Applications ..– E-commerce– Computer-aided surgery (medical applications)– Remote learning (distance education)– Computer aided Planning, Manufacturing, ... – Tourism– GIS– you name it ...
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
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
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.
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
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 natureExample 2: Air Traffic Control
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. IconicA pictorial representation of an object, an action, a property, or some other conceptrecognition, remembering, and discrimination
Main Objectives in User Interface Design
1. Increase the speed of learningmeasure: how long a new user takes to achieve certain level of proficiency.
2. Speed of Usemeasure : how long an experienced user require to perform certain task with a system
3. Reduction of errorsmeasure: the number of user errors per interaction
4. Attractive to buyers and userstarget : computer naive users
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 tasksclassify the fundamental types of information entered with interaction techniques- position- text- select- quantify
UI Design MethodsThere is no cookbook approach that ensure good interface designWhy ??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
• Examples on conflicting requirements
Want : powerful functionality But simple and clear interfaceWant: ease of use But also ease of learningWant: consistency across all aspects of the interface But
optimize operationWant intelligent and sophisticated interface But good
performance and low cost.
Results :We need methods to solve these conflicting requirements
Theories of Human Behavior
• Psychological• Sociological• Anthropological
– Develop a “Model” to help us understand and predict human behavior
– Provide simple examples of predictions
Theories of Human Social Behavior
1. Explanatory theories2. Empirical theories3. Dynamic Models
Study them and the way they support design
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 needsExample 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.
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 :
Where k is a constant
)1( log += nkT
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.
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
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 50-200 msec Average: 100 mscognitive 25-170 msec Average: 70 msmotor 70-100 msec Average: 70 ms
3. Dynamic Models
Fitts LawThis 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.
)/2log( WAKT =
Design of the User Interface
Factors that must be considered1. 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 organized4. How the package to be documented and
explained to the user
Components of the User Interface
• User Model• Command Language• Menu Format• Feedback Methods• Output Format.
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.
2. Command Language
Must be as natural as possible for the user to learnminimize 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
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
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 processingExample : Mis-spelled words in Window 9x are underlined with red color
5. Output Format
Information presented to the user1. Output pictures2. Menus3. Messages4. Other forms of dialogue generated by
the system
5. Output Format-2
Format Design to achieve greatest effectiveness1. Icon and symbol shapesSimple and clear picture of the object or operation they represent2. Screen Layout
main components(a) main area(b) Menu area(c) Display prompts and feedback area.
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 AreaMenu
Prompts and feedback messages
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
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
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 111-2222 vs. 359-2741
– 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)
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
Types of Theory in HCI
• Exploratory theoriesTo explain observed human behaviorcan provide useful insights in design lack predictive power
• Empirical lawsSimple quantitative predictions of human performance (example: Fitts law for the time taken to point to a target of a particular size).
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.
Theory of ActionAction 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 actiondeciding planning translating executing
Stage 2 - Corresponding steps after actionperceiving recognizing interpreting evaluating
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
Gulf of Execution and Gulf of Evaluation
• Gulf of ExecutionIs the difference between the intention of the person and the perceived allowable action.
• Gulf of EvaluationIs the difference between the cisible state of the system and the correct interpretation of the state of the system.
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.
Methodology Phases
• Scoping• Functional Specifications• Design• Development• Testing/Implementation
• Scoping
Business Requirement
Analysis
UserProfile
HW & SWDefinition
Project Plan
BusinessDefinition
Scoping
Adding Human factors to Software Development
ApplicationProject Team
User InterfaceGroup
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.
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