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Human Computer Interaction

Week 4Human-Computer Dialogue

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Introduction

Dialogue the process of communication

between two or more agents Dialogue Style

the way users provide input and systems present output over time.

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How to select a Dialogue Style The users’ tasks The users’ characteristics The systems’ characteristics The available input and

output devices

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Dialogue Styles

Menu system in control

Form Fill-in Direct Manipulation Command Language Natural Languageuser in control

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Menu The users read a list of items,

selected the most appropriate for their tasks, apply the syntax to indicate their selection, confirm the choice, initiate the action, and observe the effect

Examples: Pull Down Menu Pop Up Menu

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Menu Advantages Shortens Learning Reduces keystrokes Structures decision making Appropriate for novice or

intermittent users Easy to use No need to remember many things

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Menu Disadvantages Danger of many menus May slow frequent users Consumes screen space

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Menu Design Guidelines Make meaningful groupings Make meaning sequences of items in a menu Items should be brief and consistent Permit type-ahead, jump-ahead, or other

short-cuts Permit jumps to previous menu Use consistent layout and terminology Help facilities Kieger (1984) suggested: 4-8 items, 3-4

levels

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Form Fill-in Users see a display of related

fields, move a cursor among the fields, and enter data when desired

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Form Fill-inAdvantages Simplifies data entry requires modest

training Assistance is

convenient Permits use of form

management tools Appropriate for

knowledgeable intermittent users or frequent users

Disadvantages Consumes screen

space Often assume

errorless performance

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Form Fill-in Guidelines Meaningful Title / Prompt Comprehensive instructions Logical grouping and sequencing of

fields Visual appealing layout Consistent terminologies & abbreviations Error correction for characters and fields Visual templates for common fields Help facilities

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Direct Manipulation First coined by Shneiderman

(1987) to refer to interfaces which include windows, icons, menus, and pointers (WIMP interface)

The users interact directly with the object of interest on a graphics screen while the system provides rapid feedback to the users

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Direct Manipulation Advantages

Visually present task concept

Easy to learn Easy to retain Errors can be

avoided Encourage

exploration High subjective

satisfaction

Disadvantages May be hard to

program Require graphics

display and pointing devices

Power user constrained

Icon: semantic mapping

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Direct Manipulation Features (1) Explicit action: the user points at and manipulates

objects on the screen Immediate feedback: the results of the user’s action

are immediately visible (e.g. selecting an icon) Incremental effect: user action have an analogue /

sequential dimension (e.g. dragging an icon) Intuitive interaction: interaction matches the user’s

conceptual model of how the system should operate and the display shows pictures of familiar objects

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Direct Manipulation Features (2) Learning by onion peeling: the complexity of

the system is gradually revealed in layers as the user explores system facilities

Reversible action: all actions can be undone by reversing the sequence of manipulations

Pre-validation: only valid interactions have an effect, so that if the user points at an object and this makes no sense in terms of the current task, nothing happens on the display

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Command Language Command language originate with

operating systems Users issue a command and wait for

the system to respond If the result is correct, the next

command is issued If not, corrective action will be taken

by the users

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Command Language Advantages

Flexibility Appeals to

“power” users Support for user

initiative Convenient for

creating over defined macros

Disadvantages Poor error

handling Requires

substantial training and memorization

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Command Language Guidelines

Create explicit model of objects or actions Choose meaningful, specific, distinctive

names Try for hierarchical structure Prove consistent structure Support for consistent abbreviation rules Offer infrequent users the capacity to create

macros Consider command menu on high-speed

displays Limit number of commands and ways to

accomplishing a task

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Natural Language

Advantages Relieves burden of

learning syntax

Disadvantages Requires clarification

dialogue May require more

keystrokes May not show

context Unpredictable

The systems responds to arbitrary natural language sentences and phrases

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Cognitive Issues in Direct Manipulation The Gulf of Execution

Refers to the distance between the user’s goals and the means of achieving them through the system.

The Gulf of Evaluation Refers to the distance between the

system’s behavior and the user’s goals.

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Bridging the gulfs The users can bridge the gulf of execution

through changing the way they currently think and carry out the task toward the way the system requires it to be done.

The designers can bridge the gulf of execution by designing the input characteristics to match the users’ psychological capabilities.

The users can bridge the gulf of evaluation by changing their interpretation of the system image and evaluating it with respect to their goals.

The designers can bridge the gulf of evaluation by changing the output characteristics of the system.

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Expanding the notion of directness Semantic directness concerns the

relationship between what the user wants to express and the meaning of the expressions available at the interface.

Articulatory directness concerns the relation between the meanings of expressions and their physical form.

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The Primary Design Principles Affordances

Perceptual, Sequential, and Sound. Constrains

Physical, Semantic, Cultural, and Logical. Mappings

Good Mappings: appear natural and intuitive to the users.

Feedback Sending back to the user information about

what action has actually been done and what result has been accomplished.

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Further Reading Preece, Chapter 13