Laws Of Interface Design

1. Laws Of Interface Design

2. 1. User Control • The interface will allow the user to perceive that they are in control and will allow appropriate control.

3. 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.

4. 1. User Control • User who feel in control can do • Predict what the comptuer 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 accommdate the computer’s interface

5. 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

6. 2. Human Limitation • The interface will not overload the user’s cognitive, visual, auditory, tactile or motor limits.

7. 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 (864) 656-4846. • “The Magical Number Seven, Plus or Minus Two” (Miller, 1956)

8. 2. Human Limitations • Decision Making • People give early evidence too much. 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.

9. 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)

10. 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.

11. 2. Human Limitations • Motor • People can not hit targets that are too small on the screen. • 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.

12. 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)

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

14. 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.

15. 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

16. 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

17. 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

18. 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

19. 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.

20. 4. Accommodation • The interface will fit the way each user group works and thinks.

21. 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.

22. 5. Linguistic Clarity • The interface will communicate as efficiently as possible.

23. 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.

24. 5. Linguistic Clarity • Context • The language is related to the nature or context of the application. • 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.

25. 6. Aesthetic Integrity • The interface will have an attractive and appropriate design.

26. 6. Aesthetic Integrity • Refers to the issue of preference. • It is not pssible 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).

27. 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?

28. 7. Predictability *** • The interface will behave in a manner such that users can accurately predict what will happen next.

29. 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.

30. 8. Interpretation *** • The interface will make reasonable guesses about what the user is trying to do.

31. 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.

32. 9. Accuracy • The interface will be free from errors.

33. 9. Accuracy • Complete accuracy is impossible. • The goal is to significantly reduce errors. • Error reduction techniques will be discussed later.

34. 10. Technical Clarity • The interface will have the highest possible fidelity.

35. 10. Technical Clarity • Refers to the level of quality or fideltiy 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.

36. 11. Flexibility • The interface will allow the user to adjust the design for custom use.

37. 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%.

38. 11. Flexibility • Speech examples of flexibility. • Barge-in • Abiltiy to exit to an operator • Users can customize menus

39. 12. Fulfillment • The interface will provide a satisfying user experience.

40. 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 • The interface is surprisingly good

41. 13. Cultural Propriety • The interface will match the user’s social customs and expectations.

42. 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.

43. 13. Cultural Propriety • Cultural Propriety can be accomplished using User Centered Design.

44. 14. Suitable Tempo • The interface will operate at a tempo suitable to the user.

45. 14. Suitable Tempo • User Centered Design will accomplish a suitable tempo.

46. 15. Consistency • The interface will be consistent.

47. 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” would be inconsistent.

48. 16. Forgiveness *** • The interface will make actions recoverable.

49. 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.

50. 17. Responsiveness *** • The interface will inform users about the results of their actions and the interface’s status.