Chapter 1

Introduction

Human–computer interaction (HCI), alternatively man–machine interaction (MMI) or computer–human interaction (CHI) is the study of interaction between people (users) and computers.

Intro

• What is a user interface?• Why do we care about design?

• We see this all the time. – What’s good about the design of this error box?

• The user knows there is an error– What’s poor about the design of this error box?

• Discouraging• Not enough information• No way to resolve the problem (instructions or contact info)

What is Human Computer Interaction

“Human-computer interaction is a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use and with the study of major phenomena surrounding them”

Human-computer interaction

• Human-computing interaction (HCI) concerns the study of the design, evaluation, and implementation of the interfaces between computing devices and people

• HCI also often refers to the interaction itself

• HCI has three components: the human, the interaction, and the computer

HumanHumans are limited in their capacity to process information. This has important implications for DesignInformation 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• Working Memory• Long-Term Memory

Input/Output channels

Vision• Two stages in vision

– physical reception of stimulus– processing and interpretation of stimulus

• The physical apparatus: the eye– mechanism for receiving light and transforming it into

electrical energy– light reacts from objects; their images are focused

upside-down on retina– retina contains

• rods for low light vision and cones for color vision– ganglion cells

• detect pattern and movement

Hearing• Provides information about environment: distances,

directions, objects etc.• Physical apparatus:

– outer ear | protects inner and amplifies sound– middle ear | transmits sound waves as vibrations to

inner ear– inner ear | chemical transmitters are released and

cause impulses in auditory nerve• Sound

– pitch | sound frequency– loudness | amplitude– timbre | type or quality

Hearing (cont)

• Humans can hear frequencies from 20Hz to 15kHz

• Auditory system filters sounds - can attend to sounds over background noise.

Touch

• 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:– auditory - 150 ms– visual - 200ms– pain - 700ms

Memory

There are three types of memory function.

Memory

• Sensory memory– Three types:

• iconic - visual stimuli• echoic - aural stimuli• haptic - touch stimuli

– Constantly overwritten.– Information passes from sensory to STM

by attention.

Memory• Short-term memory (STM)

– Scratch-pad for temporary recall• rapid access - 70ms• rapid decay - 200ms• calculate 35 x 6 in your head• limited capacity of memory

• Short-term memory (STM)– chunking – composite items– Recency effect - easier to remember items most

recently added to STM

Memory• Long-term memory (LTM)

– Repository for all our knowledge• slow access - 1/10 second• slow decay, if any • huge or unlimited capacity

– Two types• episodic – events and experiences• semantic - structured memory of facts,

concepts, skills– Information in semantic LTM derived from episodic

LTM.

Long-term memory (cont.)

• Semantic memory structure – provides access to information– represents relationships between bits of information– supports inference

• Model: semantic network– inheritance - child nodes inherit properties of parent

nodes.– relationships between bits of information.– supports inference through inheritance.

ComputerThere is not much difference in Human and ComputerComputer consist of

• Input Devices• Output Devices• Memory• Processing

Computer can be Mobile,Microwave Oven or VCRs etc.

Input devices

• There exist a wide range of common devices for achieving input– Keyboard, mouse,

digitizer, microphone, …

Advanced input devices

• Some devices are not quite so common– Touch screens, handwriting

recognition

• Eye tracking (using infrared sensors) and gesture tracking (e.g. using magnetic sensors or computer vision) are two advances input systems

Display devices• Many common display devices

– Monitors and VDUs, speakers, printers• Display devices are commonly separated into

– Hard copy, which has physical permanence– Soft copy, which is transient and intangible

• Advanced display devices being developed continually– E-paper/E-ink– Retinal display

Analog and digital IO

• Computers are machines that store and process digital information

• Humans are organisms that send and receive information in a continuously varying analog format

• Any input device must convert from human analog information to computerized digital information– Similarly, display devices must convert from digital to

analog information

Explicit and implicit input

• Most conventional computer systems rely primarily on explicit input– For example typed into a keyboard or spoken into a

microphone• Increasingly context-aware systems (e.g.

location-based services) make use of implicit input– For example, a user arriving at a bus stop is

interpreted as a implicit input

Interaction

HCI is concerned with joint performance of Task by Human & Computer

Communication between The User and The System

Physical Interaction

• Interaction Devices

Conceptual Interaction

• Interaction Styles

Human-computer interaction

• HCI tackles questions concerning how people interact with computers– Are computers intuitive or complicated?– Are computers rewarding or frustrating?– How can computers be made accessible to everybody

(eg different physical abilities, different languages etc.)?

– To what extent can computer interaction be standardized?

– Are computers “user-friendly”?– What does it mean to be “user-friendly”?

Human-computer interaction

A basic goal of HCI is

– to improve the interactions between users and computers

– by making computers more usable and receptive to the user's

needs.

• A long term goal of HCI is – to design systems that minimize the barrier between the human's

cognitive model of what they want

– to accomplish and the computer's understanding of the user's task

Goals

GoalsThe main goal of HCI is Usability“It is a measure of the effectiveness, efficiency and satisfaction with which specified user can achieve specified goals in a particular environment”

Specifically, HCI is concerned with:

1.Methodologies and processes for designing interfaces

2.Methods for implementing interfaces 

3.Developing new interfaces and interaction techniques

4.Developing descriptive and predictive models and theories of interaction

GoalsA usable System is:

• Easy to Learn• Easy to Remember how to Use• Effective to Use• Efficient to Use• Safe to Use• Enjoyable To Use

Defining the User Interface

• User interface, design is a subset of a field of study

called human-computer interaction (HCI).

• Human-computer interaction is the study, planning, and

design of how people and computers work together so

that a person's needs are satisfied in the most effective

way.

.

Defining the User Interface

• HCI designers must consider a variety of factors:

– what people want and expect, physical limitations and

abilities people possess,

– how information processing systems work,

– what people find enjoyable and attractive.

– Technical characteristics and limitations of the computer

hardware and software must also be considered.

• The user interface is

– the part of a computer and its software that people can see, hear, touch, talk to, or otherwise understand or direct.

• The user interface has essentially two components: input and output.

• Input is how a person communicates his / her needs to the computer.

– Some common input components are the keyboard, mouse, trackball, one's finger, and one's voice.

• Output is how the computer conveys the results of its computations and re quirements to the user. – Today, the most common computer output mechanism is the display

screen, followed by mechanisms that take advantage of a person's auditory ca pabilities: voice and sound.

• The use of the human senses of smell and touch output in

interface design still remain largely unexplored.

• Proper interface design will provide a mix of well-designed

input and output mech anisms that satisfy the user's needs,

capabilities, and limitations in the most effective way

possible.

• The best interface is one that it not noticed, one that

permits the user to focus on the information and task at

hand, not the mechanisms used to present the in formation

and perform the task.

User Interfaces

The human computer interface (HCI) is what allows the user to communicate with the computer and is often called simply the user interface.

The three main types of user interface are;

Command-drivenMenu-drivenGraphical or GUI.

Command-driven user interfaces

To use a command-driven system to communicate with the computer, the user has to type in special command words.

Disk Operating System, or DOS is an example.

C:\Program Files\Microsoft Office\Office\Winword.exeC:\Documents and Settings\JE\My Documents\ICT\ User Interfaces.ppt

Advantages and Disadvantages of Command driven.

Disadvantages: Difficult if you don’t know command. Command-driven systems can be very unfriendly and confusing.

Advantages:

•They can be quick to use as long as the user knows the correct commands.

Menu-driven user interfacesMenu-driven systems offer the user lists of options which they can select by pressing a particular key on the keyboard.

F1 Load new programF2 Run programF3 List files on discF4 Backup optionsESC Quit

Main Menu Backup Options

F2 Make backup copyF3 Main MenuF1 Restore a file

F2 Pressed

Make Backup CopyEnter name of filefred.txtSelect drive

A COK

F4 Pressed

CANCEL

The main advantage of menu-driven systems is that they are easy to use.

The main disadvantage of menu-driven systems is getting to one particular option can often involve working through many different menu screens.

Advantages and Disadvantages.

Graphical user interfaces GUI

The most widely used type of graphical user interfaces are WIMP systems.

WIMP stands for Windows Icons Menu Pointer. Options are represented by small pictures or 'icons' arranged inside rectangular boxes called windows.

Advantages and Disadvantages of GUI’s

Advantages:They are very easy to use, especially for a beginner.

Disadvantage:Require a lot of RAMTake up a lot of hard disc space.

User interface design

•A good user interface should be user-friendly

•Consistency in operation, screen layout etc.

•Colors should be chosen carefully e.g. that are easy to see

•Sound can be used to do things such as alerting the user to problems but it should also be possible to turn it off

•On-line help is often a useful feature

The Importance of the User Interface

• A well-designed interface and screen is terribly important to our users. It is their window to view the capabilities of the system.

• It is also the vehicle through which many critical tasks are presented. These tasks often have a direct impact on an organization's relations with its customers, and its profitability.

• A screen's layout and appearance affect a person in a variety of ways. If they are con fusing and inefficient, people will have greater difficulty in doing their jobs and will make more mistakes.

• Poor design may even chase some people away from a system permanently. It can also lead to aggravation, frustration, and increased stress.

Systems Engineering Goals

• Achieve required performance by operator, control and maintenance personnel

• Minimize skill and personnel requirements and training time

• Achieve required reliability of personnel-equipment combinations

• Foster design standardization within and among systems

Systems Engineering Goals

• Proper functionality• Reliability• Availability• Security• Data Integrity• Standardization• Integration• Consistency• Portability

User-Interface Design Goals

• Time to learn• Speed of performance• Rate of user errors• Retention over time• Subjective satisfaction

Motivation for Human Factors in Design

• Life-critical systems 

Air traffic control, nuclear reactor operations, power utility control, space stations, police-fire dispatch, military command operations, medical instrument control, etc.

• Industrial and Commercial applications 

Banking, insurance, order entry, inventory management, airline and hotel reservation, car rental, utility billing, credit card systems, point of sales systems, etc.

Motivation for Human Factors in Design• Office, home and entertainment applications 

Personal computing applications, games, educational packages, information retrieval, e-mail, conferencing, accounting applications, etc.

• Exploratory, creative and cooperative systems 

Distributed web databases, collaborative writing, statistical hypothesis formation, business decision making, etc.