Paul Hibbitts
Educator, interaction design practitioner and software developer.
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
that can often assist in design decisions
Principles
Some sets of principles, such as user interface design principles,
will often conflict with each other
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
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Human Interface Design Principles – Apple
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Windows UX Design Principles – Microsoft
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Mandel’s Golden Rules of UI Design
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Nielsen’s Ten Heuristics
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Shneiderman’s Eight Golden Rules of Interface Design
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Tognazzini’s First Principles
Key Interface Design Principles
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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
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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
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Five HCI Laws For User Experience Design by Jeff Sauro. Available at http://www.measuringu.com/blog/hci-laws.php
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Interaction Design: Beyond Human - Computer Interaction, 3rd Edition by Yvonne Rogers, Helen Sharp, and Jenny Preece
- Mac OS X Human Interface Guidelines by Apple.
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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
