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C C C C C C C C C C
C C C C C C C C C C
C C C C C C C C C C
C C O C C C C C C C
C C C C C T C C C C
C C C C C C C C C C
C C C C C C C C C C
C C C C C C C C C C
C T C C C C C C C C
C C C C C C O C C C
C C C C C C C C C C
C C C C C C C C C C
Fig. 4.9 The left half of the figure shows a bunch of Cs and Ts. The right half shows a bunch of
Cs and Os. You should be able to see that the Ts pop-out from the Cs whereas the Os do not
program. The effect of flicker in system design is decreasing as the refresh rate of
most displays are so fast that flicker is becoming less of a problem.
4.4.6 Pop-Out Effects
One of the most useful applications of vision to interface design is to take
advantage of how the eye searches. One of the most useful effects is that certain
stimuli 'pop out' from other stimuli. Figure
4.9
shows that with a bunch of Cs, Ts
pop-out, and Os do not pop-out. Similar effects can be found for color, and a few
other features (Treisman and Gelade
1980
).
Figure
4.10
shows an application of this and a few other effects. First, you have
some object recognition that occurs—a car and building and perhaps some signs
are recognized. Then you have some automatic processes occur, you are expert at
reading so words appear as well, and these pop-out to a certain extent. You also
have the ability to read words, and these appear. Expertise and previous experience
also counts. If you have not heard of French Connection—UK (FCUK), your
automatic processes may read it as something else. This result is not a true pop-out
effect, but it is a related phenomenon, the word completion effect.
Providing multiple encoding of search items also helps in a visual search
(Garner
1974
). In Fig.
4.11
targets are encoded in several ways using multiple
features. Highlighting visual targets using just two discriminating features often
helps users find them, particularly if the encoding is not taught to users but is just
inherent in the interface.
Some feature differences will pop-out to users (Treisman and Gelade
1980
).
Differences in color, when there is not much color, and straight line segments in a
set of smooth curves will both pop-out. Partially open circles will not pop-out
when mixed with circles and slight changes in size will not pop-out. Figure
4.11
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