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Chapter 3

Understanding users

3.1 Introduction
3.2 What is cognition?
3.3 Applying knowledge from the physical world to the digital world
3.4 Conceptual frameworks for cognition
3.4.1 Mental models
3.4.2 Information processing
3.4.3 External cognition
3.5 Informing design: from theory to practice

Introduction
Imagine trying to drive a car by using just a computer keyboard. The four arrow
keys are used for steering, the space bar for braking, and the return key for acceler-
ating. To indicate left you need to press the F1 key and to indicate right the F2 key.
To sound your horn you need to press the F3 key. To switch the headlights on you
need to use the F4 key and, to switch the windscreen wipers on, the F5 key. Now
imagine as you are driving along a road a ball is suddenly kicked in front of you.
What would you do? Bash the arrow keys and the space bar madly while pressing
the F4 key? How would you rate your chances of missing the ball?
Most of us would balk at the very idea of driving a car this way. Many early
video games, however, were designed along these lines: the user had to press an ar-
bitrary combination of function keys to drive or navigate through the game. There
was little, if any, consideration of the user's capabilities. While some users regarded
mastering an arbitrary set of keyboard controls as a challenge, many users found
them very limiting, frustrating, and difficult to use. More recently, computer con-
soles have been designed with the user's capabilities and the demands of the activ-
ity in mind. Much better ways of controlling and interacting, such as through using
joysticks and steering wheels, are provided that map much better onto the physical
and cognitive aspects of driving and navigating.
In this chapter we examine some of the core cognitive aspects of interaction de-
sign. Specifically, we consider what humans are good and bad at and show how this
knowledge can be used to inform the design of technologies that both extend human
capabilities and compensate for their weaknesses. We also look at some of the influ-
ential cognitively based conceptual frameworks that have been developed for ex-
plaining the way humans interact with computers. (Other ways of conceptualizing