User Characteristics & Design Principles Gabriel Spitz 1 Lecture # 11

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 2

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 3

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

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

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 6

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 7

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 8

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

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 10

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 11

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 12

Using Metaphor– CD Control Gabriel Spitz 13

Using Metaphor - PIM Gabriel Spitz 14

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 15

Consistent Menu and Tool Bars Gabriel Spitz 16

Consistency is not Always Good Gabriel Spitz 17 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

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 18

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 19

Effective Feedback Gabriel Spitz 20

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 21

Poor Visibility Gabriel Spitz 22

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 23

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

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

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

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 27

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 28

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

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 30

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 31

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 32