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20 Chapter 1 What is interaction design?
I
hammer to hit a virtual nail represented on the computer screen) compared with
using a more efficient way to do the same thing (e.g., selecting an option using com-
mand keys) may require more effort but could, conversely, result in a more enjoy-
able and fun experience.
Recognizing and understanding the trade-offs between usability and user expe-
rience goals is important. In particular, this enables designers to become aware of
the consequences of pursuing different combinations of them in relation to fulfill-
ing different users' needs. Obviously, not all of the usability goals and user experi-
ence goals apply to every interactive product being developed. Some combinations
will also be incompatible. For example, it may not be possible or desirable to de-
sign a process control system that is both safe and fun. As stressed throughout this
chapter, what is important depends on the use context, the task at hand, and who
the intended users are.

elow are a number of proposed interactive products. What do you think are the key usabil-
y goals and user experience goals for each of them?
(a) a mobile device that allows young children to communicate with each other and play
collaborative games
(b) a video and computer conferencing system that allows students to learn at home
(c) an Internet application that allows the general public to access their medical records
via interactive TV
(d) a CAD system for architects and engineers
(e) an online community that provides support for people who have recently been
bereaved

Comment (a) Such a collaborative device should be easy to use, effective, efficient, easy to learn
and use, fun and entertaining.
(b) Such a learning device should be easy to learn, easy to use, effective, motivating and
rewarding.
(c) Such a personal system needs to be safe, easy to use and remember how to use, effi-
cient and effective.
(d) Such a tool needs to be easy to learn, easy to remember, have good utility, be safe, ef-
ficient, effective, support creativity and be aesthetically pleasing.
(e) Such a system needs to be easy to learn, easy to use, motivating, emotionally satisfy-
ing and rewarding.

1.6 More on usability: design and usability principles
Another way of conceptualizing usability is in terms of design principles. These are
generalizable abstractions intended to orient designers towards thinking about dif-
ferent aspects of their designs. A well-known example is feedback: systems should
be designed to provide adequate feedback to the users to ensure they know what to