HCI and Interface Design Principles

CMPT 363

You only use what you understand.
– Steve Jobs

Where Are We?

What is a Principle?

 
A principle is a commonly accepted high level guideline,
that can often assist in design decisions

Principles

 
Some sets of principles, such as user interface design principles,
will often conflict with each other

Key HCI Principles (a.k.a. Laws)

 
  • Miller's Law
  • Hick's Law
  • Power Law of Practice
  • Fitts' Law

Miller's Law

 
In 1956, George Miller published the paper "The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information"

Miller's Law

 

More recent research (Baddeley, 1986) indicates the capacity is closer to 3-4 items

 

Miller's Law

 
The ability of working memory to store short-term information can be increased by "chunking" data

Hick's Law

 
Hick's law estimates the time it takes for a person to make a choice as a result of the number of possible choices presented
 

Hick's Law

 
T = b log2(n + 1)
 
b = empirically determined constant
n = number of choices

Hicks Law

 

Copyright by respective copyright owners. Used without permission under the Fair Use Doctrine. Source: http://brightenstudios.com/blog/

Power Law of Practice

 
Mathematically expresses that performing the same physical action over a period of time tends to increase performance

Power Law of Practice


Time n = Time 1* n-.4

Time 1 is first time to perform task, n is number of trails
Time n is time to perform task after n times

Copyright by respective copyright owners. Used without permission under the Fair Use Doctrine. Source: http://www.sapdesignguild.org/community/design/laws.asp

Fitts' Law


Fitt’s law (1954) is a model of human movement

Fitt's Law


T = k log2(D/S + 0.5), k ~ 100 msec.

T = Time to move the hand to target
D = distance between hand and target
S = size of target

Activity: Fitts' Law

Compare two variations of a user interface,
based on the application of Fitts' Law





  • What we’ve covered so far  
    • Miller's Law
    • Hick's Law
    • Power Law of Practice
    • Fitts' Law
  • Coming up
    • Interface design principles

      Time for Questions

      Example Collections of
      Interface Design Principles


      • Human Interface Design Principles – Apple
      • Windows UX Design Principles – Microsoft
      • Mandel’s Golden Rules of UI Design
      • Nielsen’s Ten Heuristics
      • Shneiderman’s Eight Golden Rules of Interface Design
      • Tognazzini’s First Principles

      Key Interface Design Principles


      • Consistency
      • Engagement (i.e. user control)
      • Aesthetic integrity
      • Memory-load reduction
      • Forgiveness
      • Task suitability (i.e. task match)
      • Guidance, help

      Consistency


      Software interfaces should be visually and behaviourally consistent within themselves and with other software interfaces




      Consistency


      The user should never be asked to perform actions that are non-productive just for the sake of absolute consistency





      Engagement (i.e. User Control)


      The user, and not the computer, should initiate and control actions


      Engagement (i.e. User Control)


      Balance between providing users with the capabilities they need to get their work done and preventing them from harmful actions




      Aesthetic Integrity

       
      Visual displays should be well organized and utilize the principles of effective visual design (e.g. alignment, contrast, repetition, and proximity)



      Memory-load Reduction


      User’s memory demands should be minimized whenever possible


      Let’s now look at a case study related to reducing memory-load…











      • What we’ve covered so far  
        • Consistency
        • Engagement (i.e. user control)
        • Aesthetic integrity
        • Memory-load reduction
      • Coming up
        • Interface design review - part #1

          Time for More Questions
          and Discussion

           
           

          Activity: Interface Design Review

           

          Review your assignment #3 sketches with the following
          interface design principles:

          • Consistency
          • Engagement (i.e. user control)
          • Aesthetic integrity
          • Memory-load reduction
           

          Forgiveness


          Actions performed should be recoverableor reversible, and warnings should be provided when appropriate










          Task Suitability (i.e. Task Match)

           
          Only the information that users need should be provided, no more and no less
           


          Task Suitability


          Progressive disclosure is a technique where the complexities of the interface are “revealed” as related functionality is required







          Effective Progressive Disclosure


          • Most important/frequently used items should be immediately accessible
          • Display as little, but all required, elements
          • Give cues about how to find more functionality

          Guidance, Help


          Provide users with informative and relevant assistance to help them complete tasks







          • What we’ve covered so far  
            • Forgiveness
            • Task suitability (i.e. task match)
            • Guidance and Help
          • Coming up
            • Interface design review - part #2

              Time for Questions

              Activity: Interface Design Review

              Review your assignment #3 sketches with the following
              interface design principles:

              • Consistency
              • Engagement (i.e. user control)
              • Aesthetic integrity
              • Memory-load reduction
              • Forgiveness 
              • Task suitability (i.e. task match)
              • Guidance and Help
               

              A Word of Caution

               

              • HCI and interface design principles are only of true value when the right thing is being designed!
              • Don’t forget other critical issues, such as
                • Asking the right questions 
                • The ability to reframe design problems
                • Validating designs with the right people
               

              Summary

              • HCI principles (a.k.a. Laws)
                • Miller's Law
                • Hick's Law
                • Power Law of Practice
                • Fitts' Law
              • Interface design principles
                • Consistency
                • User engagement (i.e. user control)
                • Aesthetic integrity
                • Forgiveness
                • Memory-load reduction
                • Task suitability (i.e. task match)
                • Guidance, help

              References and Suggested Books


              • Five HCI Laws For User Experience Design by Jeff Sauro. Available at http://www.measuringu.com/blog/hci-laws.php 
              • Interaction Design: Beyond Human - Computer Interaction, 3rd Edition by  Yvonne Rogers, Helen Sharp,  and Jenny Preece
              • Mac OS X Human Interface Guidelines by Apple.
              • Refreshing Three HCI Laws: Fitts' Law, Hick's Law, and the Power Law of Practice by SAP Design Guild. Available at http://www.sapdesignguild.org/community/design/laws.asp
              • Usability of Interactive Products by Turkka Keinonen. Available at http://www2.uiah.fi/projects/metodi/158.htm
              • Windows User Experience Interaction Guidelines by Microsoft

              CMPT-363-153 HCI and Interface Design Principles

              By Paul Hibbitts

              CMPT-363-153 HCI and Interface Design Principles

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