InteractionGavin Sim

HCI Lecture 4 - 2010/11 1

Aims of this lectureLast week focused on persona

and scenario creation.This weeks aims are:

◦To introduce Interaction as a concept that links the human and the computer

◦To begin to consider designing interaction

HCI Lecture 4 - 2010/11 2

Inter - Action

A system is INTERACTIVE if a human user acts with the system in such a way that the system responds in an ACTIVE way depending on the ACT of the human user

HCI Lecture 4 - 2010/11 3

Humans INTERACT with computers in different ways

Touch◦Key presses◦Touch gestures

Voice◦Speech recognition

Actions◦Body recognition

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Increasing complexity

Multi-Modal InteractionIs where the user can interact

using more than one mode – a classic example is the combination of speech and touch – key pressing and talking at the same time

Example Designing multi-modal

interaction is difficult as there are ‘mode’ errors

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Mode ErrorsWhere the computer (and the

user) are not sure what ‘mode’ a system is in◦Example – the pen as a writing

device in a tablet system and the pen as a pointing device (opening up menus) in the same system

◦Save in speech recognition whilst doing word processing

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Interaction is complex

Norman’s modelGoals: What we

want to happenExecution: Execute

action in the worldWorld: Manipulate

objectsEvaluate: validate

action and compare results with our goal

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Goal

Execution Evaluation

World

Norman’s model

Execution◦Interaction◦Task sequence◦Physical Action

Evaluation◦See◦Evaluate◦Check

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ExecutionForming the IntentionGoals must be transformed into intentions, i.e., 

specific statements of what has to be done to satisfy the goal.  E.g., "Make a cup of tea using a Tetley tea bag."

Specifying an Action SequenceWhat is to be done to the World.  The precise

sequence of operators that must be performed to effect the intention.  E.g., “Boil the kettle....."

Executing an ActionActually doing something.  Putting the action

sequence into effect on the world.  E.g., actually boiling the kettle.

HCI Lecture 4 - 2010/11 9

EvaluationPerceiving the State of the WorldPerceiving what has actually happened.  E.g.,

the experience of taste of the tea. Interpreting the State of the WorldTrying to make sense of the perceptions

available.  E.g., Putting those perceptions together to present the sensory experience of a cup of tea.  

Evaluating the OutcomeComparing what happened with what was

wanted.  E.g., did the cup of tea match up to the requirement of 'a nice drink'?

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Gulf’s of InteractionNorman talks about 2

THE GULF OF EXECUTION:  does the system provide actions that correspond to the intentions of the user?

THE GULF OF EVALUATION:  does the system provide a physical representation that can be directly perceived and that is directly interpretable in terms of the intentions and expectations of the user?

We don’t know what to doWhat we do doesn’t take us towards our goal We don’t see any feedbackThe feedback we get doesn’t tell us we are

making progressHCI Lecture 4 - 2010/11 11

Examples…

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Example 2The problem statement is clear,

but the supplemental explanation is Martian.

Interaction is about Goals

Understand the person => Understand the goals => Understand the interaction

HCI Lecture 4 - 2010/11 14

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Keyboards and KeypadsPrimary mode of text entryBeginners 1 keystroke per

secondAverage office worker 5 strokes

per second (50 words a minute)Rapid data entry can be achieve

if more than one key can be pressed simultaneously◦Can represent entire words◦Court rooms (300 words a minute)

Interacting with computersInteract with computers in a

variety of different waysToday we will focus on keyboard

and pointing devices

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Keyboard LayoutQWERTY Keyboard Christopher

Latham in the 1870’s to prevent keys getting jammed

Used letter pairs far apart thereby increasing finger travel distanceKeyboards on Computers are thus inefficient

Keyboard LayoutDVORAK increase typing from

150 words per minute to 200 for advanced users plus reduce errors

ABCDE in alphabetical order, novices will find keys

Fitts LawCalculate effectiveness of interaction

Word Example

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KeysConcave surface and matte finish reduce

finger slipKey presses requires 40- to 125- gram force

and displacement from 1 to 4 millimetersFORCE is importantKey pressed enough emits a light click. This tactile and audible feedback is importantClicks on surface computing important as you do not have tactile feedback

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Keys mobile deviceSome come with full QWERTY

keyboardCan reach input of 60 words per

minute with both thumbs when auto corrects

Numerical keyboards◦Multitap key pressed multiple times

and pause◦Predictive techniques T9 dictionary

based◦LetterWise uses probabilities of

prefixes for example if type th probability e

next letter

MacKenzie, I. S., Kober, H., Smith, D., Jones, T., Skepner, E. (2001). LetterWise: Prefix-based disambiguation for mobile text input. Proceedings of the ACM Symposium on User Interface Software and Technology - UIST 2001, pp. 111-120. New York: ACM

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Pointing DevicesUseful for 7 types of interaction

(Foley et al 1984)◦Select - from a menu◦Position - drag picture next to text◦Orient - a picture, create motion◦Path - create a curve◦Quantify – specify numeric value e.g.

volume in music◦Gestures – indicate an action to perform◦Text – enter, edit, move

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Pointing DevicesGrouped into:

◦Direct Control◦Indirect Control

Direct Control of on screen surface such as touchscreen or stylus

Indirect Control away from the screen mouse, graphics tablets etc..

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StylusDrawingHandwrite on touch sensitive

deviceNatural way to interactDevice needs training to

recognise hand writingRecently had Vision Objects

collecting samples of hand writing

iPhone vs Wii – text input Which is faster for text input?

iPhone vs Wii – text input iPhone 18.5 wpmWii 9.2 wpmHowever – error rates

◦7.7% for the iPhone◦2.8% for Wii

Errors on the iPhone predominantly cause hitting the adjacent key

SummaryUnderstanding how users interact

is imporatntExplored different forms of

intearction◦Keyboard ◦Pointing