Usability Heuristics
CMPT 281
Outline
• Usability heuristics
• Heuristic evaluation
Usability heuristics
• Heuristics:
– rules of thumb that describe features of usable systems
• As design principles:
– broad usability statements that guide design efforts
– derived by evaluating common design problems across
many systems
• As evaluation criteria:
– the same principles can be used to evaluate a system for
usability problems
– becoming very popular
• user involvement not required
• catches many design flaws
Usability heuristics
• Advantages
– the minimalist approach
• a few guidelines can cover many usability problems
• easily remembered, easily applied with modest effort
– discount usability engineering
• cheap and fast way to inspect a system
• can be done by usability experts and end users
• Problems
– principles are at the ‘motherhood’ level
• can’t be treated as a simple checklist
• there are subtleties involved in their use
Nielsen’s Ten Heuristics
1. Visibility of system status
2. Match between system and the real world
3. User control and freedom
4. Consistency and standards
5. Error prevention
6. Recognition rather than recall
7. Flexibility and efficiency of use
8. Aesthetic and minimalist design
9. Help users recognize, diagnose, and recover from errors
10. Help and documentation
Visibility of system status
• The system should always keep users informed
about what is going on
• Appropriate feedback within reasonable time
Visibility of system status
What mode
am I in now?
What did I
select?
How is the
system
interpreting
my actions?
Visibility of system status
Match between system and real world
• The system should speak the users' language
– Words, phrases and concepts familiar to the user
– Not system-oriented terms
• Follow real-world conventions
• Put information in a natural and logical order
Match between system and real world
Match between system and real world
User control and freedom
• Users often choose system functions by
mistake
– They need clearly marked “emergency exits”
– Let them get back without extended dialogue
• Support undo and redo
User control and freedom
User control and freedom
Consistency and standards
• Users should not have to wonder whether
different words, situations, or actions mean
the same thing.
• Follow platform conventions
Consistency and standards
Ok
Cancel
Cancel
Ok
Done
Never Mind
Accept
Dismiss
Consistency and standards
Error prevention
• Even better than good error messages is a
careful design which prevents a problem from
occurring in the first place.
• Two options:
– Eliminate error-prone conditions
– Check for them and present users with a
confirmation option before they commit
Error prevention
Error prevention
Recognition rather than recall
• Minimize the user's memory load by making
objects, actions, and options visible
• The user should not have to remember
information from one part of the dialogue to
another
• Instructions for use of the system should be
visible or easily retrievable whenever
appropriate
Recognition rather than recall
Recognition rather than recall
Flexibility and efficiency of use
• Accelerators can speed up interaction for
expert users
– Accelerators are unseen by the novice user
– The system can cater to both inexperienced and
experienced users
• Allow users to tailor frequent actions.
Flexibility and efficiency of use
Aesthetic and minimalist design
• Dialogues should not contain information that
is irrelevant or rarely needed
• Every extra unit of information in a dialogue
competes with relevant units, and diminishes
their visibility
Help users recognize, diagnose, and
recover from errors
• Error messages:
– Should be expressed in plain language (no codes)
– Should precisely indicate the problem
– Should constructively suggest a solution
Help users recognize, diagnose, and
recover from errors
Help and documentation
• Best if the system can be used without help!
• May be necessary to provide help and
documentation
• Help should be:
– Brief
– Easy to search
– Focused on the user's task
– Concrete
Help and documentation
Help and documentation
Neilsen’s Nine Heuristics
•
•
•
•
•
•
•
•
•
1. Simple and natural dialog
2. Speak the user’s language
3. Minimize user’s memory load
4. Be consistent
5. Provide feedback
6. Provide clearly marked exits
7. Provide shortcuts
8. Deal with errors in a positive manner
9. Provide help
1. Simple and natural dialogue
• Use the user’s conceptual model
• Match the users’ task in a natural way
– minimize mapping between interface and task
1. Simple and natural dialogue
• Present exactly the information the user needs
– less is more
• less to learn, to get wrong, to distract...
– information should appear in natural order
• related information is graphically clustered
• order of accessing information matches user’s expectations
– remove or hide irrelevant or rarely needed
information
• competes with important information on screen
– use windows frugally
• don’t make navigation and window management excessively
complex
2. Speak the users’ language
• Terminology based on users’ language for task
– e.g. withdrawing money from a bank machine
2. Speak the users’ language
• Use meaningful mnemonics, icons, and
abbreviations
– eg File / Save
• Ctrl + S
• Alt FS
• Open folder
(abbreviation)
(mnemonic for menu action)
(toolbar icon)
2. Speak the users’ language
2. Speak the users’ language
3. Minimize user’s memory load
• Promote recognition over recall
– Computers good at remembering things, people aren’t!
– menus, icons, lists vs. command lines, field formats
– relies on visibility of objects to the user (but less is more!)
3. Minimize user’s memory load
• Input formats
– Indicate required format
– give example and default entry
3. Minimize user’s memory load
• Small number of rules applied universally
– generic commands
• same command can be applied to all interface objects
– interpreted in context of interface object
• copy, cut, paste, drag and drop
– for characters, words, paragraphs, circles, files
4. Be consistent
• Consistency of effects
– the same words, commands, and actions should always have
the same effect in equivalent situations
• increases predictability
• Consistency of language and graphics
– same information and controls in the same location
Ok
Cancel
Cancel
Ok
Done
Never Mind
Accept
– forms should follow boiler plate
– use the same visual appearance across the system
• e.g. icons, UI widgets
• Consistency of input
– consistent syntax across system
Dismiss
5. Provide feedback
• Continuously inform the user about:
– what the system is doing
– how the system is interpreting the user’s input
• The user should always know what is going on
What’s it
doing?
> Doit
> Doit
This will take
5 minutes...
Time for
coffee.
5. Provide feedback
What mode
am I in now?
What did I
select?
How is the
system
interpreting
my actions?
5. Provide feedback
• Be specific, based on user’s input
• Interpretation of feedback:
– Simpler when in the context of the action
5. Provide feedback
• Response time
– how users perceive delays
• 0.1 second: perceived as instantaneous
• 1 second: user’s flow of thought stays uninterrupted,
but delay noticed
• 10 seconds: limit for keeping user’s attention focused
on the dialog
• > 10 seconds: user will want to perform other tasks
while waiting
5. Provide feedback
• Dealing with long delays:
– Cursors/Throbbers
• for short transactions
– Percent done dialogs
• for longer transactions
– how much left
– estimated time
– what it is doing…
Contacting host (10-60 seconds)
– Random animation/Throbber
• for unknown times
cancel
6. Provide clearly marked exits
How do
I get
out of
this?
6. Provide clearly marked exits
• Users don’t like to feel trapped by the computer!
– offer an easy way out of as many situations as possible
• Strategies:
–
–
–
–
–
Cancel button (for dialogs waiting for user input)
Universal Undo (can get back to previous state)
Interrupt (especially for lengthy operations)
Quit (for leaving the program at any time)
Defaults (for restoring a property sheet)
7. Provide shortcuts
• Support experienced users
– experts should be able to perform frequent actions quickly
• Strategies:
– keyboard and mouse accelerators
•
•
•
•
•
abbreviations
command completion
menu shortcuts
function keys
double clicking vs. menu selection
– type-ahead (entering input before the system is ready for it)
– navigation jumps and hyperlinks
– history and bookmark lists
• e.g. WWW: ~60% of pages are revisits
Keyboard
accelerators for
menus
Customizable
toolbars and
palettes for
frequent actions
Split menu, with
recently used
fonts on top
Double-click
raises toolbar
dialog box
Double-click
raises objectspecific menu
Scrolling controls
for page-sized
increments
Alternate
representation for
quickly doing
different tasks
Toolset brought in
appropriate to this
representation
8. Deal with errors positively
• People will make errors!
• Errors we make
– Mistakes
• arise from conscious deliberations that lead to an error
instead of the correct solution
– Slips
• unconscious behaviour that gets misdirected en route to
satisfying goal
– e.g. drive to store, end up at the office
• shows up frequently in skilled behaviour
– usually due to inattention
• often arises from similarities of actions
Types of slips
• Capture error
– frequently done activity takes charge instead of
one intended
• occurs when common and less common actions have
the same initial sequence
– change clothes for dinner and find oneself in bed (William
James, 1890)
I can’t
– confirm saving of a file you meant to rename
believe I
pressed
Yes...
Types of slips
• Description error
– intended action has much in common with others that are
possible
• usually occurs when right and wrong objects physically near each
other
– pour juice into bowl instead of glass
– go jogging, come home, throw sweaty shirt in toilet instead of laundry
basket
– move file to trash instead of to folder
• Data-driven error
– the data for the intended action is similar to other data
• more common data pushes itself forward
– telephone home instead of correct number
Types of slips
• Loss of activation error
– forgetting what the goal is while undergoing the sequence
of actions
• start going to room and forget why you are going there
• navigating menus/dialogs and can’t remember what you are
looking for
• can sometimes continue action to remember (or go back to
beginning)!
• Mode errors
– people do actions in one mode thinking they are in
another
• insert / edit mode in vi
• refer to file that’s in a different directory
• look for commands / menu options that are not relevant
Designing for slips
• General rules
– Prevent slips before they occur
– Detect and correct slips when they do occur
– User correction through feedback and undo
• Examples
– mode errors
• have as few modes as possible (preferably none)
• make modes highly visible
– capture errors
• instead of confirmation, make actions undoable
• allows reconsideration of action by user
– e.g. trash can can be opened and “deleted” file taken back out
Designing for slips
• Examples continued
– loss of activation errors
• if system knows the goal, make it explicit
• if not, allow person to see path taken so far
– description errors
• in icon-based interfaces, make sure icons are not too
similar
• check for reasonable input
Design approaches for errors
• General idea: forcing functions
– prevent or mitigate the continuation of wrongful action
• Gag
– deals with errors by preventing the user from continuing
• e.g. cannot get past login screen until correct password entered
• Warn
– warn people that an unusual situation is occurring
– when overused, becomes an irritant
• e.g.,
– audible bell
– alert box
Design approaches for errors
• Do nothing
– illegal action just doesn’t do anything
– user must infer what happened
• enter letter into a numeric-only field (key clicks ignored)
• put a file icon on top of another file icon (returns it to
original position)
• Self-correct
– system guesses legal action and does it instead
– but leads to a problem of trust
• spelling corrector
Design approaches for errors
• Let’s talk about it
– system initiates dialog with user to come up with
solution to the problem
• compile error brings up offending line in source code
• Teach me
– system asks user what the action was supposed to
have meant
– action then becomes a legal one
A problematic error message to a nuclear power plant operator
8. Deal with errors positively
• Provide meaningful error messages
– error messages should be in the user’s language
• preferably task language
– don’t make people feel stupid
•
•
•
•
Try again, bonehead!
Error 25
Cannot open this document
Cannot open “chapter 5” because the application “Microsoft
Word” is not on your system
• Cannot open “chapter 5” because the application “Microsoft
Word” is not on your system. Open it with “Teachtext”
instead?
8. Deal with errors positively
• Prevent errors
– try to make errors impossible
– modern widgets: only “legal
commands” selected, or “legal
data” entered
• Provide reasonableness checks
on input data
– e.g. on entering order for office
supplies:
• “5000 pencils is an unusually
large order. Do you really
want to order that many?”
9. Provide help
• Help is not a replacement for bad design!
• Simple systems:
– walk up and use; minimal instructions
• Most other systems:
– feature rich
– some users will want to become
“experts” rather than “casual” users
– intermediate users need reminding,
plus a learning path
Types of help
• Tutorials and getting started manuals
– short guides that people are likely to read when
first obtaining their systems
• encourage exploration and getting to know the system
• try to give main concepts and essential syntax
– on-line tours, exercises, and demos
• demonstrates very basic functionality through working
examples
Types of help
• Reference manuals
– used mostly for detailed lookup by experts
• rarely introduces concepts
• thematically arranged
– on-line hypertext
•
•
•
•
search / find
table of contents
index
cross-index
Types of help
• Reminders
– short reference cards
• expert user who just wants to check facts
• novice who wants to get overview of system’s capabilities
– keyboard templates
• show shortcuts and syntactic meanings of keys
• promotes recognition vs. recall
– tooltips
• floating text over graphical items indicates their function or
purpose
Heuristic Evaluation
• Helps find usability problems in a UI design by
systematic inspection
• Small set (3-5) of evaluators examine UI
– independently check for compliance with usability
principles (“heuristics”)
– different evaluators will find different problems
– evaluators only communicate afterwards
• findings are then aggregated
• Can perform on working UI or on sketches
Inspection methods
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•
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Systematic inspection of a user interface
Goal is to find usability problems
Inspections use inspectors not real users
Works for systems at any stage:
– paper or code prototypes
– working systems
• Heuristic evaluation:
– the most popular inspection technique
Phases of Heuristic Evaluation
• Pre-evaluation training
– give evaluators needed domain knowledge & information
on the scenario
• Evaluation
– individuals evaluates UI & makes list of problems
• Severity rating
– determine how severe each problem is
• Aggregation
– group meets & aggregates problems (w/ ratings)
• Debriefing
– discuss the outcome with design team
Heuristic Evaluation Details
• Each inspector works alone with the interface
– A session typically lasts 1-2 hours
• The two-pass approach
– first pass: focus on specific interface elements
– second pass: higher level integration and flow
• If system is walk-up-and-use or evaluators are domain
experts, no assistance needed
– otherwise might supply evaluators with scenarios
• Each evaluator produces list of problems
– explain why with reference to heuristic or other
information
– be specific & list each problem separately
Severity Rating
• Used to allocate resources to fix problems
• Estimates of need for more usability efforts
• Combination of
– frequency
– impact
– persistence (one time or repeating)
• Should be calculated after all evals. are complete
• Should be done independently by all judges
Severity Rating
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•
•
•
•
0 - don’t agree that this is a usability problem
1 - cosmetic problem
2 - minor usability problem
3 - major usability problem; important to fix
4 - usability catastrophe; imperative to fix
Severity Ratings Example
[Heuristic “Consistency”, Severity=3]
The interface used the string "Save" on the first screen
for saving the user's file, but used the string "Write file"
on the second screen. Users may be confused by this
different terminology for the same function.