Design and Interaction, Part 2

31 January 2006Kathy E. Gill

Our goal : flow

The process of an optimal experience The activity feels seamless It is intrinsically enjoyable Individual loses self-consciousness

Eight Golden Rules of Interface Design (1/3)

Strive for consistency (the most frequently violated rule): • Terminology • Prompts • Menus • Help screens • Color • Layout • Capitalization • Fonts

Eight Golden Rules of Interface Design (2/3)

Let frequent users use shortcuts • Abbreviations • Special keys • Hidden commands • Macro facilities

Offer informative feedback Design dialogs to yield closure

• Sequences of actions should be organized into groups

• Beginning, middle, and an end

Eight Golden Rules of Interface Design (3/3)

Offer error prevention and simple error handling

Permit easy reversal of actions Support internal locus of control Reduce short-term memory load

Effective navigation

Clearly communicates Where am I? Where have I been? Where can I go?

Navigation icons

Should not require explanation Must represent the correct concept Must be visually distinct Are appropriately sized Text (label) is often the best visual cue

Menus (1/2)

Types• Static, pull down, fly-out, pop-up• Recognition, not recall (memory)

Menu organization • Alphabetical• Chronological• Categorical

Menus (2/2)

Provide real-estate savings• But have invisible info

Pull-down, fly-out• Horizontal or vertical

Pop up menus• Appear at various places on the screen

Bridging Gulf of Execution

Hick’s Law : number of choices directly affects the size of the Gulf of Execution

Fitt's Law : time required to acquire a target is a function of the distance to, placement of, and size of the target.

How does this relate to navigation?

KISS

Remember each bit of info competes with other bits

Eliminate irrelevant information

From The Interface Hall of Shame http://www.iarchitect.com/tabs.htm

What not to do!

The Humane Interface

“An interface is humane if it is responsive to human needs and considerate of human frailties.”• Raskin, The Humane Interface (6)

Requires knowledge of how humans and machines operate

Object-Action Model of Interaction

Understand tasks • Evaluate real-world objects and the actions

applied to those objects Create interface representations

• Objects and actions Make interface actions visible to users

Task Hierarchies

Computer system designers must generate a hierarchy of objects and actions (the interaction) that successfully models user tasks:

Representations in pixels on a screen Representations in physical devices Representations in voice or other audio cue

Semantic Understanding

Understand how the process works, the meaning of an action• A mouse click• A submit button

Syntactic Understanding

Understand the specific rules of behavior that achieve an action• In Windows, double-click on a file to launch

(open) the application and load file• On the Web, single-click an underlined

word to go to a new Web page

When Syntax Vanishes (1/2)

We are forced to maintain a profusion of device-dependent details in our memory. • Which action erases a character?• Which abbreviations are permissible? • Which of the numbered function keys

produces the previous screen?

When Syntax Vanishes (2/2)

Learning, use and knowledge retention is hampered when details vary across systems unpredictably

Syntactic knowledge is learned through repeated usage  

Syntactic knowledge is system dependent -- our visitors perceive “the Web” as a system, violate only after careful deliberation

Our Job

To minimize syntactic/memory burdens• Familiar objects and actions represent their

task objects and actions• Standard (or de facto standard) widgets

Why the mailbox did not work as early e-mail icon - not cross-cultural

Five Tests of Effectiveness (1/2)

Time to learn How long does it take for typical members of the community to learn relevant task?

Speed of performance How long does it take to perform relevant benchmarks?

Rate of errors by users How many and what kinds of errors are commonly made during typical applications?

Five Tests of Effectiveness (2/2)

Retention over time Frequency of use and ease of learning help make for better user retention

Subjective satisfaction Allow for user feedback – interviews (focus groups), online surveys (both free-form comments and satisfaction scales).

Design for Diversity

Personality differences Cultural and international diversity Users with disabilities Elderly users Anything else?

Raskin’s Rules

The user should set the pace of the interaction

Error avoidance, facilitated with “undo/redo”

Accessible to the naïve, efficient for the expert

Errors are not mistakes!

Mistakes are the result of conscious deliberation

Slips result from automatic behavior• Norman’s Types: capture, description,

data-driven, associative activation, loss-of-activation and mode errors

Good Error Messages

Polite Illuminating Treat the user with respect

Design for Error

Minimize occurrence by understanding the causes of errors

Make detection and recovery easier Change the attitude toward error from

“stupid user” to “stupid design”

One small problem:

When you design an error-tolerant system, people come to rely on that system (it had best be reliable!)• Anti-lock brakes (ABS)• Blade guard on circular saw• Anything else?

To increase errors, add a little:

Social pressure Time pressure Economic pressure

In other words, real life!

Resultant design philosophy:

Put knowledge in the world (iow,make options visible)

Remember the three questions:• Where am I, where can I go, where have I

been? Design for errors

The End!

Apologies for the background noises as I advanced the slides in outline view … one take only and I don’t have Jyotsna’s production skills. :)