Introducing User-Centered Systems Design - Foundations for Designing User-Centered Systems - page 20

Table 1.6 Example cognitive level issues
How do users decide where to look for information?
What information do users need to develop a strategy for performing a particular task? Do they
need absolute or relative values?
How much experience do the users have with the task and with the interface?
What is the user's mental model of the interface and task (which will often differ from the
designer's or the observer's mental model of the same interface and task)?
Is there so much noise and interruption that users cannot process information, for example, the
interruptions in the Kegworth aircraft crash?
How can users tell if things are not going well? What feedback do they get? What strategies are
available to the user when the system goes wrong?
How can we ensure that users do not lose their ability to perform the task manually as a result of
automation?
How can word processors be made more accessible to novice users or casual users? How do these
factors change when the systems considered are more complex?
A better understanding of how users think and feel can be used to create better
designs. An improved system can come from understanding the mental effort
involved in tasks in terms of the information processing mechanisms (architecture)
that support our thinking, including constraints such as how many arbitrary
symbols users can remember. These issues may help us to understand how com-
plex devices with high functionality (e.g., personal video recorders) can be made
more accessible to non-expert users by providing information, by guiding the user,
and by not asking them to perform difficult tasks (like remembering more than
their short-term memory can hold).
For example, consider the fairly common task of determining differences
between two or more items. Imagine you had two dials to read, each with a
different number, and these numbers varied randomly. Your task is to press a
button when the difference between the two numbers exceeds 10. This task would
require you to process the information from both dials, make a mental calculation
and evaluate whether the difference exceeds 10. The existence of a third dial which
just showed the difference would make your task easier and faster, removing the
need for the mental calculation (the cognitive effort).
1.4.4 Social Factors
The final level is the social level. How do users interact with other people in
relation to their task? In some cases this interaction will be to work on the task
jointly with others using the computer to support and mediate their communica-
tion. In other cases, users will ask other users for help in understanding systems, or
will use the system for, or with others (such as bank tellers, loan officers, and
airline pilots), or the interaction could be constrained by some regulatory authority
(as in aviation and the nuclear power industry).