User Characteristics & Design Principles

1. User Characteristics & Design Principles Lecture # 11 Gabriel Spitz

2. Objective of this lecture • Describe a set of important UI design principles • Place these principles within the context of human characteristics and show how they contribute to usability Gabriel Spitz

3. Achieving Usability • Our objective in designing the User Interface is to achieve a high degree of usability for our product • User Centered Design (UCD) recommends early and ongoing iterations with users • To optimize the design process we should attain as high degree of usability as we can on our first design cycle • Usability principles can help us achieve such a high degree of usability early in the design Gabriel Spitz

4. Usability and Product Success • Ignoring usability can impact the bottom line and safety MS BOB Renault 4 circa 1970 Users rejected anthropomorphisms Negative transfer of training resulting in many errors Gabriel Spitz

5. Effective interaction is determined by the goodness of fit between interface design and operator’s characteristics, needs, task requirements Quality of the Interaction - Usability Martijnvan Welie (2001) Gabriel Spitz

6. What is a UI Design Principle • Knowledge gained from past design experience and usability studies • It’s a guide post pointing the way to a usable design • It is not by itself an end or a rule • One should try and follow it when it makes sense, and deviate from it when needed Gabriel Spitz

7. UI Design Principles • Know your user • Let the user control the interaction • Capitalize on what the user already knows • Maintain consistency at the interface • Provide effective feedback • Expose the interaction to the user • Minimize reliance on user memory • Minimize the impact of user error • Aesthetic matters • Always test your interface with users Gabriel Spitz

8. 1) Know Your User – S/he is not you • Effective user interface is one that is compatible with and focuses on the users and their tasks. It considers: • General human characteristics • Characteristics the users of your application • Domain specific vocabulary • Computer literacy • General education • Task specific characteristics of your users • Touch typists • Frequency of task performance Gabriel Spitz

9. Self Check-In Kiosk Designed for the general traveling population – What can you assume about the users of this system? Gabriel Spitz

10. 2) Let the User Control the Interaction • People want to control their environment • Software applications should be designed to support the users, their task, and their interaction style • Constraining users’ action is fine • Controlling users’ action should be avoided • Controllability can impact user satisfaction Gabriel Spitz

11. Ways to Increase User Control • Limit the extent to which users are forced to perform a task in a predetermined way • Minimize the use of Modes • Always allow users to cancel out • Allow users to save partial work such as forms Gabriel Spitz

12. 3) Capitalize on what Users Know • Using metaphors or familiar idioms (cut & paste) at the interface will enable users to instantly understand the details of the application • Reusing knowledge will significantly enhance learning or reduce the amount of learning needed to achieve proficiency Gabriel Spitz

13. Using Metaphor– CD Control Gabriel Spitz

14. Using Metaphor - PIM Gabriel Spitz

15. 4) Maintain Consistency • Consistency enables users to anticipate events and reuse learned behaviors -Positive Transfer • It is achieved by reusing UI design structures within and between applications • Complying with standards for example • Reuse of knowledge reduces learning and enhances performance Gabriel Spitz

16. Consistent Menu and Tool Bars Gabriel Spitz

17. Consistency is not Always Good Usability is maximized by reusing usable elements – Duplicating bad design will result in a consistently bad design This is a poor design for water temperature control and rinsing soapy hands Gabriel Spitz

18. When Inconsistency is Good • Inconsistent structure or design can be used to attract user attention and prevent an automated response e.g., The delete dialog box Gabriel Spitz

19. 5) Provide Effective Feedback • Feedback closes the action loop and “enables” the user to continue with his/her task or sequence of actions • Effective feedback is feedback that is provided to users: • Immediately following the user’s action • At an appropriate level • E.g., Action, Context, System state level • At an appropriate place • E.g., at the locus of attention • Feedback improves performance and learning Gabriel Spitz

20. Effective Feedback Gabriel Spitz

21. 6) “Expose” the Interaction to the User • Let the user see clearly the functions that are available at the interface • Exposing the interaction facilitates learning and performance Gabriel Spitz

22. Poor Visibility Gabriel Spitz

23. 7) Minimize Reliance on Memory • Ability of users to recall commands, object names, sequence of actions, etc. is limited • Make the interface visual with limited reliance on recall • Allow selection rather than relying on users to remember a command or object name • Exceeding memory limits hinders performance-errors and speed Gabriel Spitz

24. Supporting Memory Limitation One way of supporting memory limitation is to use name recognition Gabriel Spitz

25. Supporting Memory Limitation A better way of supporting memory limitation is to capitalize on both name recognition and visual recognition Gabriel Spitz

26. Supporting Memory Limitation Another way of supporting memory limitation with both name recognition and visual recognition Gabriel Spitz

27. 8) Minimize the Impact of Error • Cost of errors impacts user performance • We are all afraid to err or loose our work • When possible enable users to reverse their actions • Undo • Confirm delete • Else, limit the cost of error • Auto Save • But don’t over protect the user • Easy recovery from errors enhances user satisfaction and performance Gabriel Spitz

28. 9) Aesthetics Matter • Consider function first, form later • But don’t ignore form • Form or presentation often sets the moods of the user which in turns impacts users’ experience • Form or presentation facilitates: • Visual scanning of a dialog box, window, page • Location or detection of objects • Aesthetics enhances user satisfaction and performance Gabriel Spitz

29. Poor Aesthetics Poor alignment Inconsistent use of colors Also poor task flow Gabriel Spitz

30. Use Colors carefully • Use of color to convey information in the interface should be accompanied with clear secondary cues • If red vs. green is the only way to tell which section is within bounds, about 6% of all users will have trouble telling the difference (9% Male, 2% Female) • Everyone is colorblind in low light Gabriel Spitz

31. 10) Always Test Your Interface • We don’t have strong models of the human operator/user • We can not predict (but can anticipate) how certain design attributes will effect performance or satisfaction • We use testing to assess and refine our designs Gabriel Spitz

32. Lecture’s Main Points • Effective interaction design is built on understanding how human act and the factors that impact human activity within a given context • Many of these factors have been captured by UI design principles • Adhering to these design principles will significantly enhance the usability of an interface Gabriel Spitz