IntrIntroduction

Introduction to Human Computer Interaction

Preeti Mishra

Course Instructor

What is HCI

Short for human-computer Interaction, This discipline is concerned with the study, design, construction

and implementation of human-centric interactive computer systems.

Building specific functionality into computers and the long-term effects that systems will have on humans.

concerned with the application design and engineering of the human interfaces

Various Perspectives

sociology and anthropology are concerned with the way that human systems and technical systems mutually adapt to each other;

ergonomics is concerned with the safety of computer systems and the safe limits of human cognition and sensation;

psychology is concerned with the cognitive processes of humans and the behaviour of users;

linguistics is concerned with the development of human and machine languages and the relationship between the two.

Definition

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.”

8 Guidelines for creating good human computer interaction

1 Strive for consistency.Consistent sequences of actions should be required in similar situations; identical terminology should be used in prompts, menus, and help screens; and consistent commands should be employed throughout.

2 Enable frequent users to use shortcuts.As the frequency of use increases, so do the user's desires to reduce the number of interactions and to increase the pace of interaction. Abbreviations, function keys, hidden commands, and macro facilities are very helpful to an expert user.

Cont..

3 Offer informative feedback.For every operator action, there should be some system feedback. For frequent and minor actions, the response can be modest, while for infrequent and major actions, the response should be more substantial.

4 Design dialog to yield closure.Sequences of actions should be organized into groups with a beginning, middle, and end. The informative feedback at the completion of a group of actions gives the operators the satisfaction of accomplishment, a sense of relief, the signal to drop contingency plans and options from their minds, and an indication that the way is clear to prepare for the next group of actions.

Cont..

5 Offer simple error handling.As much as possible, design the system so the user cannot make a serious error. If an error is made, the system should be able to detect the error and offer simple, comprehensible mechanisms for handling the error.

6 Permit easy reversal of actions.This feature relieves anxiety, since the user knows that errors can be undone; it thus encourages exploration of unfamiliar options. The units of reversibility may be a single action, a data entry, or a complete group of actions.

Cont..

7 Support internal locus of control.Experienced operators strongly desire the sense that they are in charge of the system and that the system responds to their actions. Design the system to make users the initiators of actions rather than the responders.

8 Reduce short-term memory load.The limitation of human information processing in short-term memory requires that displays be kept simple, multiple page displays be consolidated, window-motion frequency be reduced, and sufficient training time be allotted for codes, mnemonics, and sequences of actions.

Importance of Good Interface.

Importance..

System users often judge a system by its interface rather than its functionality

Good User Interface Design can be the difference between product acceptance and rejection in the marketplace

If end-users feel it is not easy to learn, not easy to use, or too cumbersome, an otherwise excellent product could fail.

Importance..

Big Improvements can establish new products, companies, markets …

Biggest enemy of good interface design is time

Guidelines

UI Designers should have the ability to adjust an application’s layout to the “mental map” users consult while working with it. This “map” corresponds to the user’s expectations, past experiences and overall learning style;

Goal is to make complex information easy to understand.

User Centered Design

User Interface Design Process

Design Principles

Principle Description

User Familiarity Interface should use terms familiar to users

Consistency Comparable operations should be started the same way

Minimal Surprise Users should never be surprised

Recoverability Users should be able to recover from their errors

User Guidance Meaningful feedback, context-sensitive help

User Diversity Should provide for different types of user

To accomplish these design principles there exists various theories…

Nielsen’s Ten Usability Heuristics

Visibility of system status Match between system and the real world User control and freedom Consistency and standards Error prevention Recognition rather than recall Flexibility and efficiency of use Aesthetic and minimalist design Help users recognize, diagnose, and recover from errors Help and documentation

Galitz’s Heuristics (Table 14.2)

Automate unwanted workload Reduce uncertainty Fuse data Present new info with meaningful aid to interpretation Use names that are conceptually related to functions Group data in consistently meaningful ways to reduce search

time Limit data-driven tasks Include in displays only info needed by user at a given time Provide multiple coding of data where appropriate Practice judicious redundancy

Galitz’s WWW Heuristics

Speak the user’s language Be consistent Minimize the user’s memory load Build flexible and efficient systems Design aesthetic and minimalist systems Use chunking Provide progressive levels of detail Give navigational feedback Don’t lie to the user

Notion: Human

Human:

Input / output channel Senses Responders/ Effectors Human memory: how it works, how they

learn, make mistakes How the above study will help in design

of computer systems

Input- Output Channel

Human have 5 major senses: sight, hearing, touch, smell, taste

Of these sight, hearing and touch are important in our context( others may be important in augmented reality systems)

There are effectors: limbs, fingers, eyes, head, and vocal system, which play role in typing, mouse control, voice, eye, head and body position

Human “Eye”

Based on human visual study system we can deduce: Ability to read falls of inversely as the distance form

point of focus increases It sets limits on the amount that can be seen or read

without moving eyes A user concentration on middle of screen cannot be

expected to read help text on the bottom line We see movement well at edge of our vision, thus

moving icons will be distracting

Perceiving:

Size and depth( visual angle)

Size of object matters to know its distance

Brightness( larger the display the more it will appear to flicker usually if less than 50hz)

Color: hue intensity and saturation

Color

Hue: wavelength, we can see 150 hues Blue shortest hue and red longest Intensity: brightness of color Saturation in amount of whiteness in color By varying above three humans can perceive 7

million colors

Visual processing:

Humans process distance by size of object

And perceive same color even with varying brightness

We also consider the context

Proofreading illusion and optical illusion

the quick brown

fox jumps over the

the lazy dog

Reading

Perception of text is important for HCI While reading there are 2 processes:

Eye makes jerky movements(saccades) Fixation Perception occurs during fixation Eye moves backwards and forward if text is complex

this is called regressions Adults read about 250 words per minute, by either

reading few characters, analyzing shape

Because, therafter, henceforth Floccinaucinihilipilification, a

ntidisestablishmentarianism or honorificabilitudinitatibus

Reading

Speed at which text can be read is called legibility Positive contrast increases legibility but it will be

more prone to flicker

Hearing

Human ear can hear frequencies from 20hz to 15 khz It can distinguish frequency changes of less than 1.5 hz

at low freq but is less accurate at high frequency Auditory system allows some filtering of sounds

received, allowing us to ignore background noise and concentrate on important information

Sound could be used in HCI to convey information about system state

Touch (haptic perception)

Gives vital information about information This field is important to notice experience of user

towards computer generated objects Its critically important for visually challenged people

where interface is designed in Braille

Apparatus of touch

Skin contains 3 types of receptors: Thermoreceptors(head and cold) Nociceptors(pressure heat and pain) Mechanoreceptors(pressure)

They serve for rapid adaption for response and response towards static positions

Eg: for typist the relative placement of fingers and feedback from keyboard are important

Upcoming e-commerce based application

Having realistic shopping experience Can visit www.novint.com

Movement

Movement time involves following action: Stimulus of que is received through sensory receptors and

transmitted to brain Que is processed with valid response generation Brain tells appropriate muscles to respond

The above process depends on: Skill of user( like in video games) Age of user

Considering Movement While Designing Interactive Systems

Time taken to move a particular target on screen Fitts law: movement time=a+blog2(dist/size+1)

a and b are empirically determined constants Thus user find it difficult to manipulate:

Small objects Distance moved

Our arms, wrists, and fingers busy themselves on the keyboard and desktop; our head, neck, and eyes move about attending to graphic details recording our progress. Matching the movement limits and capabilities of

humans with interaction techniques on computing systems,

Human memory

Three types of memory buffers: Sensory memory Short term/ working memory Long term memory

Try out

Elephant Tiger Caterpillar Dog Horse Cow Hen Earthworm Butterfly frog

Sensory Memory

To process an information, we should first obtain it. (If we make an analogy with computers we can think of this as the initial input stage to the computer. In order to write it to the hard disk, first the information

should be entered by means of an input device.) This memory is very short and temporary. We tend to

forget everything we get from these senses. For instance our eye takes around 12 frames/sec. meaning that

we have on the average 12*60*60*16(hours we are not sleeping) = 691.200 frames/day.

When we pay our attention, information is passed onto our short-term memory.     

Short Term Memory

Next stage is short-term memory, also known as working memory.

This is a concentrated stream of incoming knowledge, which is available until we pay our attention to another subject.  

Long Term Memory

Long-term memory (LTM) is the permanent memory and available to us for a quite large period of time. Sigmund Freud separates LTM to 2 parts:

Preconscious: Knowledge in our permanent memory. In order to reach there the information needs to be recalled, however the knowledge is reachable using normal recalls (although this recall may last 2 seconds or 2 years!!).

Unconscious: This is the knowledge we obtained, however we do not know that we know it!!! In order to obtain it, we need to have specific methods like hypnosis. We are unable to reach this knowledge with our own methods.

Long Term Memory

We can categorize LTM knowledge as: Declarative: This is used to identify and categorize

everyday objects we meet and events we live. 1.A) Episodic: It is the personal life experience which turns out

to be "good old day memories". Important both consciously and subconsciously in our future actions.

1.B) Semantic: It is the general concept of objects around us, each object has certain specifications in its class. Semantic knowledge helps us to identify that object and distinguish it from other objects. For instance we can distinguish whether the object is a 5 year old child or a 60 year old adult.

Long Term Memory

Procedural: This is a step-by-step knowledge on how to realize a certain accomplishment.

Imagery: This is pictorial view of the things we have seen, for instance a beautiful painting van gogh

Processing Information

Level of processing theory:     This theory tells that the endurance of the information is also

dependent on the depth of learning process. There are different levels of information processing, the deeper we examine a subject the more we learn about it.

Parallel Distributed theory:  This theory asserts that information processing is done through

multiple parallel paths in our mind rather than being a single process. Knowledge is represented in a distributed fashion rather than a single location. When we obtain information about a subject we are gathering information about the subject we focus onto and information about the sub-branches at the same time while strengthening the main subject with these branches.

Processing Information

Connectionist Approach: This approach also defines knowledge representation as a

distributed group of units in the mind. However in this approach, these units are individually meaningless. A unit is activated by stimulations coming from other units and sends a transfer function to the neighbour units. From the union of these activations knowledge may be recalled or formed.

Memory : HCI

You just use your fast processing short-term memory without making any transition to long-term memory.

Don’t overload the short term memory frequently his short-term memory is not enough. In this

case the usage of multiple windows acts as a local cache for the user improving his capacity to wander around the main topics and then to recall back on the local windows he needs to concentrate. These types of layouts are known as cognitive layouts, as they support cognitive processing capacity of the user

Computer

Input devices

Output devices

Work out

What input and output devices would you use for the following systems? For each, compare and contrast alternatives and if appropriate indicate why the conventional keyboard, mouse and CRT system may be less suitable Portable word processor Tourist information system Tractor mounted crop spraying controller

Memory

Memory

Processing and Networks

Finite processor speed in case of standalone processors Factors that limit the speed of interactive system:

Computation bound Storage channel bound Graphics bound

Networked Computing

generic term in computing which refers to computers or nodes working together over a network.It may also mean: Cloud computing Distributed computing Virtual Network Computing

Interaction

Y Interaction?

We have seen about human and computer

We don’t need to deal with them individually

So we have to learn about communication between human and

computer : Interaction

Purpose of Interactive system

Aid users to achieve some GOALS in some DOMAIN by performing some TASK

Task need to be analyzed to (task analysis): Identify the problem space Use our knowledge of task and goals to assess the

interactive system that is designed

The execution: evaluation cycle(Norman’s Model)

Human formulates a plan of action which is executed at computer interface

Norman proposed that actions are performed in cycles such as Establishing a goal ; Executing the action; Evaluating the results.

The above are subdivided into seven different stages

Norman’s Model

Establish the goal Forming the interaction Specifying the action

sequence Executing the action Perceiving the system state Interpreting the system

state Evaluating the system state

w.r.to the goals and intentions

1. Use both knowledge in world & knowledge in the head 2. Simplify task structures. 3. Make things visible 4. Get the mapping right (User mental model = Conceptual Model = Designed Model) 5. Convert constrains into advantages (Physical constraints, Cultural constraints, Technological constraints) 6. Design for Error 7. When all else fails – Standardize

Norman’s HCI model

Norman’s HCI model consists of three types: User’s Mental Model ; System Image Model ;

Conceptual Model.

System Model

How various devices in system behave their characteristics..

Conceptual Model

The Conceptual Model. This is the technically accurate model of the computer / device / system created by designers / teachers/researchers

Ideally, the design model and user model have to be as close as possible for the systems acceptance.

The designer must ensure that the system image is consistent with and operates according to the proper conceptual model.

Levels of abstraction based on Interaction Model

As a basis for his Interaction Model Norman proposed the following levels of abstraction of knowledge of the user : Task Level Goal Level Semantic level Syntax level Lexical level Physical Level.

Till now we have learned..

Introduction to the subject HCI Importance of good User Interface Importance of good design, Design principles

Notion: Human Computer Interaction( Norman’s Interaction Model)

The above learning mapped to

Course Outcome 1 and 2

End of Unit 1