Usability is not an add-on
Steven Pemberton
CWI, Amsterdam
A thought experiment
What are the features of websites that you go back to regularly, that differentiate them from websites with the same purpose?
Differentiating features
Forrester did some research on this
Good content (75%)
Usability (66%)
Speed (58%)
Frequency of updating (54%)
(the rest is noise: 14% and lower)
Surprises
User testing is the first item to go when looking for reduced costs
Many web-building companies have no usability experts on their staff
Many web-building companies build sites that are measurably unusable
Software
Usability is just as important for software
Although the usability advantage has less effect than with websites, it still plays a role via word-of-mouth (E.g. Quicken)
It definitely improves the quality of software for the user
Why do we use programs?
To get a task done
A program is seldom an end in itself
Any interruption in the task, because you have to think about the interface, is a failure of the interface
The task
Task is the word used in user interface circles to refer to whatever it is you are trying to achieve
There is always a task (even when vegging out in front of the TV)
Tasks are usually (unconsciously) split by the user into sub-tasks (and so on)
The user
The user is always right!
If the user fails to achieve something because of the interface, it is the interface’s fault: it doesn’t address that sort of user
Most programs choose to address some range of users
What is usability?
Usability can be summarised as three factors:
Efficiency:
how quickly you achieve what you want
Effectiveness: how correctly you achieve it
Satisfaction: how much you enjoy doing it
Why Usability?
People using your software will work faster
They will produce better results
They will be happier
More people will buy your software
Compromises
Sometimes usability factors have to be balanced out:
An experiment with 3 chess-playing interfaces (command-line, mouse, and real manipulation of chess pieces) showed that the mouse was the fastest
But with real manipulation, the user won more often (was more effective)
Games deliberately reduce your efficiency
Surprises
The psychology of human beings can cause some surprising results:
In a test with three methods of writing (pen on paper, a text editor, a word processor) users wrote less with a pen but of a higher quality, more with a text editor but of a lower quality, and more with a word processor but with a higher quality.
Transparency
A fourth aim of user interfaces is transparency: you don’t notice a good user interface, you spend all your time solving the problem.
Not just buttons and menus!
A typical lay-error is to think that user interfaces are just about buttons and menus
This is just surface (and largely uninteresting)
More interesting is function (what you can do) and attitude
Learnability vs Ease of use
Another lay-error is to think that Usability is only about making programs easy-to-use for beginners
While this is an admirable aim, it may get in the way of efficiency, effectiveness and/or satisfaction of expert users (who may be your major class of users)
This probably explains the success of emacs
Interfaces are everywhere
It is wrong to think that user interfaces are the exclusive domain of computer software
It is worth adopting a critical attitude to the user interfaces of everything
Interfaces are everywhere
It is wrong to think that user interfaces are the exclusive domain of computer software
It is worth adopting a critical attitude to the user interfaces of everything
Warning: this can ruin the rest of your life...
Bad everyday interfaces
Doors are a good example of everyday interfaces that often are bad:
Doors that suggest they need to be pulled, but actually need to be pushed
They often use a simple help system: PUSH
A good door interface doesn’t need this
Bad everyday interfaces 2
Typical cookers have 4 burners, and 4 switches organised in a different way, that therefore need a help system (little pictures) to help you use them
Bad everyday interfaces 3
And so it goes on and on…
Unprogrammable video players
Hi-fi’s where the on-light is not next to the on-off switch
Light switches on the hinge side of the door
… (think of some more yourself)
Bad interfaces
Bad interfaces come between the user and the task
They create a new sub-task: how do I get round this problem
The ownership of interfaces
Programmers often have a similar attitude to their programs to that of parents towards their children: they can do no wrong
It can be very hard to persuade programmers that there is something wrong with their program’s interface
Factors in usability
There are many dimensions to usability, for instance:
Psychology
Culture
International issues
(Dis)/ability levels
etc.
Usability is not an add-on
Since function and attitude are determining factors of usability, trying to make a program usable post facto may only produce a local optimum
Build usability in from the start
Employ usability experts
Involve them from the start
Plan to build iteratively
User test regularly
User tests need only be small: 7 users will smoke out most remaining problems
Make the programmers watch the usability tests
Usability: Where do I get it?
Get your attitude from
Don Norman The Design of Everyday Things
Bruce Tognazzini Tog On Interface
Books by Edward Tufte
Get your information from
The annual CHI conference
ACM interactions
Get your people from/send them to
ACM SIGCHI and SIGCHI.NL