Cognition: Mental Representations, Problem Solving, and Decision Making - Foundations for Designing User-Centered Systems - page 163

MAIN
ACCUMULATOR

MA

ENERGY
BOOSTER
ONE

ENERGY
BOOSTER
TWO

LASER
BANK

SA

SECONDARY
ACCUMULATOR
ONE

EB1 EB2

SA1

Off On

SA2

SECONDARY
ACCUMULATOR
TWO

POWER
SOURCE

Fig. 6.1 A type of circuit schematic (based on Ritter and Bibby 2008 )

6.2.1 Simple Representations

Representations can be classified in many ways. Two types of simple represen-
tations that occur repeatedly include semantic/propositional representations and
visual/spatial representations.
Consider the information in Table 6.1 , and attempt to memorize it. Then
consider the information in Fig. 6.2 . The information represented is the same in
both places, but the representations give rise to different behavior and support
different types of tasks.
The information about the sets of letters in Table 6.1 and Fig. 6.2 is probably
better represented as a series rather than as a set of propositions—it is more
succinct, easier to learn, and for most tasks it is easier to manipulate. The
canonical series ABCD is particularly easy to memorize: it probably already exists
as a series in your head. The other series is more difficult, but is probably easier to
remember and use as a series than as a set of propositions.
The best representation for the workshop expenses will vary. For most tasks,
users will be better off with the numbers themselves. The graphical representation
on the left in Fig. 6.2 (created using the default settings of a common spreadsheet
program) is less clear than the bespoke graph on the right in the same figure. The
relative values can be quickly judged, but the absolute numbers will be more dif-
ficult to obtain. Both graphs are less useful than a table of numbers for many tasks.
Sometimes users will use propositional representations. Sometimes they will
use a more visual representation. Interfaces should support the representation that
users have, as well as be mindful of supporting the representation that will be most
helpful for a task. It is the job of the designer to find the representations that best
support the task, and those that users already have, and to balance the design to
support these representations.