Introducing User-Centered Systems Design - Foundations for Designing User-Centered Systems - page 15

Often your population of users will be heterogeneous, and if you are not aware
of this heterogeneity you could end up disenfranchising large sections of your
users. We have worked with web sites that now incorporate text versions so that
they can also support the visually impaired (through screen readers and descrip-
tions of pictures), and users that access the web via low speed connections, such as
dialup lines or from very remote locations (Ritter et al. 2005 ). Neither of these
types of users is likely to be the same as many designers.
Although there is no general solution to the question of when to stop analyzing
the user and start building the system, Pew and Mavor's ( 2007 ) approach provides
a subjective answer. In their risk driven approach, the risks to success are
re-evaluated as the design process progresses. In some cases, progress with the
technology is the largest risk to success; in others, not knowing the user and their
tasks will be the largest risk. So Pew and Mavor's answer is that you should study
the user and their tasks until the risk of not knowing more about them is lower than
the other risks to success. As noted above, we will return to describe this approach
in more detail in the final chapter, Chap. 14 .

1.4 Summarizing Design Relevant User Characteristics:
The ABCS Framework

The purpose of this topic is to help you to come up with principled opinions about
what designs are most likely to be effective. We introduce the idea of design
relevant user characteristics. Attempts to define a complete list of human char-
acteristics stretch from hundreds (e.g., Brown 1988 ) to thousands of pages (Boff
and Lincoln 1988 ; Salvendy 1997 ). Table 1.2 offers some examples that are often
discussed, taken from Brown ( 1988 ).
To help organize design relevant human characteristics, we offer a framework
that we call the ABCS. The abbreviation represents four aspects of users that often
need to be examined when designing systems:
A

Anthropometrics: the shape of the body and how it influences what is
designed; consideration of the physical characteristics of intended users such
as what size they are, what muscle strength they have, and so on

B Behavior: perceptual and motivational characteristics, looking at what people

can perceive and why they do what they do

C Cognition: learning, attention, and other aspects of cognition and how these

processes influence design; users defined by how they think and what they
know and what knowledge they can acquire

S Social factors: how groups of users behave, and how to support them through

design; users defined by where they are—their context broadly defined
including their relationships to other people.
We now briefly explain each of these areas in more detail.