ITCS 6010 Laws Of Interface Design. 1. User Control The interface will allow the user to perceive...

ITCS 6010

Laws Of Interface Design

1. User Control

The interface will allow the user to perceive that they are in control and will allow appropriate control.

1. User Control

There is a difference between feeling in control and actually being in control.

Our goal is the user should feel in control.

1. User Control

User who feel in control can: Predict what the computer will do next Take the next action they decide is

appropriate at their choice Go back and fix problems Work the way they want to, not changing their

work to accommodate the computer’s interface

1. User Control

VUI users can feel the lost of control quickly because the computer is speaking and may take control of the conversation

Solutions Barge-in, allow the user to interrupt the agent Error recovery for speech errors

2. Human Limitation

The interface will not overload the user’s cognitive, visual, auditory, tactile or motor limits.

2. Human Limitations

Memory People can remember 5 – 9 things for about

20 seconds in their short term memory, unless the information is chunked, i.e. phone numbers (704) 687-7988.

Adding semantic meaning “The Magical Number Seven, Plus or Minus Two” (Miller, 1956)

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2. Human Limitations

Decision Making People give early evidence too much significance. If

they receive 1 piece of information early, they believe it over what they hear later.

People do not extract as much information out of the data they have.

People are more sure of their decision as they get more information, even if the quality of the information is bad.

2. Human Limitations

Decision Making People seek more information than they can

actually handle or extract data from. People can only deal with 3 or 4 hypotheses at a

time. People focus only on a few attributes. People seek information that confirms a decision

they have already made. Engineering psychology and human performance (Wickens, 1984)

2. Human Limitations

Visual People do not read everything on a screen, page

or window. People will not find information on a full or

cluttered screen. People are easily distracted by visual stimuli such

as graphics, animations or too much information. People have trouble reading fonts that are too

small or vary in style too much.

2. Human Limitations

Motor People can not hit targets that are too small on

the screen. People may have trouble double-clicking. People do not always realize they can or should

drag and drop. People do not like constantly switching between a

mouse and keyboard. People need time to adapt to new input devices.

2. Human Limitations

Speech People have more trouble remembering

messages spoken in synthetic speech versus natural speech, unless trained to do so.

Use slow speech to increase user encoding of messages (this is for novice users).

3. Modal Integrity

The interface will fit individual tasks within whatever modality is being used: auditory, visual, or motor/kinesthetic.

3. Modal Integrity

Some tasks are best performed using speech, others using vision or others with motor/kinesthetic or tactile modes.

Some are best performed using multiple modes.

3. Modal Integrity

Auditory modality is best when Information is short and simple Information is needed immediately, but not later

(doesn’t have to be remembered) Information is temporal in nature (refers to events

over time) The message is a critical warning A verbal response is required

3. Modal Integrity

Auditory modality is best when The visual system of the person is already

overextended The environment is not conducive to a visual

display (i.e. driving a car) The person needs to stay “dark adapted” The person needs to be moving continually

3. Modal Integrity

Visual modality is best when Information is complex and long Information needs to be remembered The information deals with spatial relationships,

i.e. maps The person’s audition is overextended The environment is noisy

3. Modal Integrity

Visual modality contradictions Information is complex and long

People summarize information when it is large Information needs to be remembered

Seven plus or minus 2 The information deals with spatial relationships,

i.e. maps People deal with verbal navigation well

3. Modal Integrity

The average time it takes a person to hear a signal and make a simple response is 150 milliseconds.

The average time it takes a person to see a signal and make a simple response is 200 milliseconds.

Robert Bailey, Human performance engineering. 1982.

4. Accommodation

The interface will fit the way each user group works and thinks.

4. Accommodation

The system should adapt or accommodate itself to the user, not the other way around.

This is accomplished using a User Centered-Design approach.

5. Linguistic Clarity

The interface will communicate as efficiently as possible.

5. Linguistic Clarity

Refers to the clarity of the language of the application, not the clarity of the monitor.

An interface has linguistic clarity when it provides context and speaks in the user’s terminology.

5. Linguistic Clarity

Context The language is related to the nature or context of

the application. Example:Equipment Instructions:

First, sort the items into like categories. Sorting by color is common, but you can also use the other characteristics, such as texture or type of handling needed. Once you have sorted the items, you are ready to use the equipment. You want to process each category from the sorting separately.

5. Linguistic Clarity

Context The language is related to the nature or context of

the application. Example:Using Your New Washing Machine:

First, sort the items into like categories. Sorting by color is common, but you can also use the other characteristics, such as texture or type of handling needed. Once you have sorted the items, you are ready to use the equipment. You want to process each category from the sorting separately.

5. Linguistic Clarity

Context Spoken words can lose context quickly versus

words that appear as labels on a screen.

Terminology The language uses terms that are familiar to the

user.

6. Aesthetic Integrity

The interface will have an attractive and appropriate design.

6. Aesthetic Integrity

Refers to the issue of preference. It is not possible to separate human performance

from preference.

A study showed that users preferred a voice that was casual and used the first person, I, compared to others (Susan Boyce 1999).

6. Aesthetic Integrity

Normally, people prefer natural voices, but synthetic voice are more appropriate for warnings and alerts (Cohen & Oviatt 1994).

Alert, Alert …

How may I help you?

7. Predictability ***

The interface will behave in a manner such that users can accurately predict what will happen next.

7. Predictability

Users Mental Model = Conceptual Model This makes the interface predictable.

Predictability is crucial to speech interfaces. If your interfaces is not predictable, then the help

or instructions must be exceptional, which is difficult because of human memory. There is only so much you can say before they user forgets what was said.

8. Interpretation ***

The interface will make reasonable guesses about what the user is trying to do.

8. Interpretation

The system should be able to monitor user behavior and make a reasonable guess as to the action or speech the user is trying to apply Speech recognition plays a huge role in

interpretation. Misinterpretations are a problem. Context aware systems can help enhance

interpretation.

9. Accuracy

The interface will be free from errors.

9. Accuracy

Complete accuracy is impossible.

The goal is to significantly reduce errors. Error reduction techniques will be discussed later.

10. Technical Clarity

The interface will have the highest possible fidelity.

10. Technical Clarity

Refers to the level of quality or fidelity of the interface. Visual interfaces with technical clarity have high

resolution and easy to view graphics. Kinesthetic interfaces have buttons that are easy

to discern and easy to press. Speech interfaces will have sounds and speech

of high quality.

11. Flexibility

The interface will allow the user to adjust the design for custom use.

11. Flexibility

Allows users to customize the interface for their own work. Differs from accommodation, which adjusts the

interface to match the way users work.

Accommodation accounts for what 80% of the users need to do 80% of the time.

Flexibility accounts for the other 20%.

11. Flexibility

Speech examples of flexibility. Barge-in Ability to exit to an operator Users can customize menus

12. Fulfillment

The interface will provide a satisfying user experience.

12. Fulfillment

User has a satisfying experience with the interface. We will discuss how to measure this using the

PARADISE Framework later.

Fulfillment techniques Offer a better way to do something Performs basic tasks effectively Match current work process

13. Cultural Propriety

The interface will match the user’s social customs and expectations.

13. Cultural Propriety

User now expect that their computers will interact with them the way humans do. People treat machines like people (Reeves & Nass, The

Media Equation, 1995)

Users may understand they are speaking with a computer and not a person, but that does not mean that they expect any less. This does mean that they may become more

tolerant of errors.

13. Cultural Propriety

Cultural Propriety can be accomplished using User Centered Design.

14. Suitable Tempo

The interface will operate at a tempo suitable to the user.

14. Suitable Tempo

Important due to temporal nature of speech Pace too slow => frustrated user Pace too fast => confused user

User Centered Design will accomplish a suitable tempo.

15. Consistency

The interface will be consistent.

15. Consistency

If the interface is inconsistent, this limits predictability.

Example “Go Forward” is an acceptable command,

therefore, it is consistent to use “Go Back” or “Go Backwards”.

“Last” or “Previous” would be inconsistent.

16. Forgiveness ***

The interface will make actions recoverable.

16. Forgiveness

We must assume that errors will occur, and therefore build mechanisms into the interface to handle the errors in as forgiving a way as possible. We will discuss error handling and forgiveness in

more detail later.

17. Responsiveness ***

The interface will inform users about the results of their actions and the interface’s status.

17. Responsiveness

Users need feedback on their actions and feedback on the system’s actions. Feedback is especially important in VUI.

Responsiveness in speech When should the user speak? Who’s turn is it to speak?

Responsiveness is related to User Control.

Laws Of Interface Design These laws serve as a guideline to interface development

in general.

We will discuss more specific VUI design guides next.