Page 93 - Designing Sociable Robots

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74 Chapter 6

Behaviorally, the robot will continue to search upon encountering a static object of high
raw saliency but of the wrong feature. Upon encountering a static object possessing the right
saliency feature, the robot successfully terminates search and begins to visually engage the
object. However, the search behavior sets the attention gains to allow Kismet to attend to
a stimulus possessing the wrong saliency feature if it is also supplemented with motion.
Hence, if a person really wants to attract the robot’s attention to a specific target that the
robot is not actively seeking out, then he/she is still able to do so.
During engagement, the gains are set so that Kismet slightly prefers those stimuli pos-
sessing the favored feature. If a stimulus of the favored feature is not present, a stimulus
possessing the unfavored feature is sufficient to attract the robot’s attention. Thus, while en-
gaged, the robot can satiate other motivations in an opportunistic manner when the desired
stimulus is not present. If, however, the robot is unable to satiate a specific motivation for
a prolonged time, the motive to engage that stimuli will increase until the robot eventually
breaks engagement to preferentially search for the desired stimulus.

Effect of Gain Adjustment on Looking Preference
Figure 6.8 illustrates how top-down gain adjustments combine with bottom-up habituation
effects to bias the robot’s gaze. When the seek-people behavior is active, the skin-tone
gain is enhanced and the robot prefers to look at a face over a colorful toy. The robot
eventually habituates to the face stimulus and switches gaze briefly to the toy stimulus.
Once the robot has moved its gaze away from the face stimulus, the habituation is reset and
the robot rapidly reacquires the face. In one set of behavioral trials when seek-people
was active, the robot spent 80 percent of the time looking at the face. A similar affect can
be seen when the seek-toy behavior is active—the robot prefers to look at a toy (rather
than a face) 83 percent of the time.
The opposite effect is apparent when the avoid-people behavior is active. In this case,
the skin-tone gain is suppressed so that faces become less salient and are more rapidly
affected by habituation. Because the toy is relatively more salient than the face, it takes
longer for the robot to habituate. Overall, the robot looks at faces only 5 percent of the
time when in this behavioral context. A similar scenario holds when the robot’s avoid-toy
behavior is active—the robot looks at toys only 24 percent of the time.
Socially Manipulating Attention

Figure 6.9 shows an example of the attention system in use, choosing stimuli that are
potentially behaviorally relevant in a complex scene. The attention system runs all the time,
even when it is not controlling gaze direction, since it determines the perceptual input to
which the motivational and behavioral systems respond. Because the robot attends to a