Page 80 - Designing Sociable Robots

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6 The Vision System

Certain types of spontaneously occurring events may momentarily dominate his attention or cause him
to react in a quasi-reflex manner, but a mere description of the classes of events which dominate and
hold the infants’ sustained attention quickly leads one to the conclusion that the infant is biologically
tuned to react to person-mediated events. These being the only events he is likely to encounter which
will be phased, in their timing, to coordinate in a non-predictable or non-redundant way with his own
activities and spontaneous reactions.
—J. Newson (1979, p. 207)

There are a number of stimuli that infants have a bias to attend to. They can be catego-
rized according to visual versus auditory sensory channels (among others), and whether
they correspond to social forms of stimulation. Accordingly, similar percepts have been
implemented on Kismet because of their important role in social interaction. Of course,
there are other important features that have yet to be implemented. The attention system
(designed in collaboration with Brian Scassellati) directs the robot’s attention to those visual
sensory stimuli that can be characterized by these selected perceptions. Later extensions to
the mechanism could include other perceptual features.
To benefit communication and social learning, it is important that both robot and human
find the same sorts of perceptual features interesting. Otherwise there will be a mismatch
between the sorts of stimuli and cues that humans use to direct the robot’s attention versus
those that attract the robot’s attention. If designed improperly, it could prove to be very
difficult to achieve joint reference with the robot. Even if the human could learn what
attracts the robot’s attention, this defeats the goal of allowing the person to use natural and
intuitive cues. Designing for the set of perceptual cues that human infants find salient allows
us to implement an initial set that are naturally significant for humans.

6.1 Design of the Attention System

Kismet’s attention system acts to direct computational and behavioral resources toward
salient stimuli and to organize subsequent behavior around them. In an environment suit-
ably complex for interesting learning, perceptual processing will invariably result in many
potential target stimuli. It is critical that this be accomplished in real-time. In order to deter-
mine where to assign resources, the attention system must incorporate raw sensory saliency
with task-driven influences.
The attention system is shown in figure 6.1 and is heavily inspired by the Guided Search
v2.0 system of Wolfe (1994). Wolfe proposed this work as a model for human visual search
behavior. Brian Scassellati and I have extended it to account for moving cameras, dy-
namically changing task-driven influences, and habituation effects (Breazeal & Scassellati,
1999a). The accompanying CD-ROM also includes a video demonstration of the attention
system as its third demo, “Directing Kismet’s Attention.”

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