Display and Interface Design

Semantic Mapping versus Proximity Compatibility 227
effective at representing detailed, precise information. Thus, if the exact value
of an individual variable is needed for any purpose (e.g., monitoring a critical
value, communicating its value to others, completing a checklist, or providing
input to software modules), it should be represented using digital values.
The appropriate design strategy is to combine these two representational
forms by annotating the geometrical form with digital values. This is made
explicit in the findings of the Bennett and Walters (2001) study described earlier.
The presence of an analog configural display (see Figure 9.13a–e) was
necessary for successful control of a process control system (a complicated
divided-attention task). On the other hand, providing digital values was
clearly the most effective design strategy for improving performance at the
focused-attention task. The composite display, with both types of information,
was clearly the most effective display when overall performance at both
divided- and focused-attention tasks is considered. Bennett and Walters conclude
that “participants could select and use the specific design features in the
composite display [configural display, digital values] that were appropriate
for tasks at each boundary [divided- and focused-attention tasks]” (p. 431).
Hansen (1995) echoed these sentiments and takes the logic one step further:
“Human factors researchers should not treat the discussion of graphical versus
analytical (e.g., numerical) interfaces as an either/or issue. Instead, they should
be studying ways to improve the integration of these interfaces” (p. 542). See
Calcaterra and Bennett (2003) for a study investigating just how the process of
annotating geometrical forms with digital values should proceed.
9.6 PCP Revisited
Our analysis of PCP until this point has been limited to its initial conceptualization.
Wickens and Carswell (1995) proposed a revised version of
PCP, noting that the original “strong form of the PCP interaction, shown in
Figure la [Figure 9.1], does not emerge from many experimental results” (p.
490). A major change was the incorporation of principles of design based
on configurality and emergent features (Wickens and Carswell 1995). These
conceptual changes moved PCP to a closer approximation of our semantic
mapping approach; the changes are the most likely source of the confusion
and misinterpretation referred to in the beginning of this chapter. Despite
these changes, we believe that these two approaches are fundamentally different
and we will conclude this chapter by describing why.
One fundamental difference is that the revised version of PCP has retained
the organizing principles of “object integration,” which are identified as
one of the four fundamental processing mechanisms or “forces underlying
the effects observed in the PCP” (Wickens and Carswell 1995, p. 485). The
concept of a perceptual object still plays a fundamental role: Wickens and
© 2011 by Taylor & Francis Group, LLC