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.

Door

Good User Interface

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

Correspondence

Graphic Interface

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.