Page 233 - Designing Sociable Robots

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214 Chapter 12

Another advantage is robustness. A system that integrates action, perception, attention,
and other cognitive capabilities can be more flexible and reliable than a system that focuses
on only one of these aspects. Adding additional perceptual capabilities and additional con-
straints between behavioral and perceptual modules can increase the relevance of behaviors
while limiting the computational requirements. For example, in isolation, two difficult prob-
lems for a visual tracking system are knowing what to track and knowing when to switch
to a new target. These problems can be simplified by combining the tracker with a visual
attention system that can identify objects that are behaviorally relevant and worth tracking.
In addition, the tracking system benefits the attention system by maintaining the object
of interest in the center of the visual field. This simplifies the computation necessary to
implement behavioral habituation. These two modules work in concert to compensate for
the deficiencies of the other and to limit the required computation in each.
Using the human visual system as a model, a set of design criteria for Kismet’s visual
system can be specified. These criteria not only address performance issues, but aesthetic
issues as well. The importance of functional aesthetics for performance as well as social
constraints has been discussed in depth in chapter 5.

Similar visual morphology Special attention has been paid to balancing the functional
and aesthetic aspects of Kismet’s camera configuration. From a functional perspective, the
cameras in Kismet’s eyes have high acuity but a narrow field of view. Between the eyes,
there are two unobtrusive central cameras fixed with respect to the head, each with a wider
field of view but correspondingly lower acuity.
The reason for this mixture of cameras is that typical visual tasks require both high acuity
and a wide field of view. High acuity is needed for recognition tasks and for controlling
precise visually guided motor movements. A wide field of view is needed for search tasks,
for tracking multiple objects, compensating for involuntary ego-motion, etc. As described
earlier, a common trade-off found in biological systems is to sample part of the visual field
at a high resolution to support the first set of tasks, and to sample the rest of the field at
an adequate level to support the second set. This is seen in animals with foveal vision,
such as humans, where the density of photoreceptors is highest at the center and falls off
dramatically towards the periphery. This can be implemented by using specially designed
imaging hardware (van der Spiegel et al., 1989; Kuniyoshi et al., 1995), space-variant image
sampling (Bernardino & Santos-Victor, 1999), or by using multiple cameras with different
fields of view, as with Kismet.
Aesthetically, Kismet’s big blue eyes are no accident. The cosmetic eyeballs envelop the
fovea cameras and greatly enhance the readability of Kismet’s gaze. The pair of minimally
obtrusive wide field of view cameras that move with respect to the head are no accident,
either. I did not want their size or movement to distract from Kismet’s gaze. By keeping