Page 234 - Designing Sociable Robots

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Social Constraints on Animate Vision 215

these other cameras inconspicuous, a person’s attention is drawn to Kismet’s eyes where
powerful social cues are conveyed.
Similar visual perception For robots and humans to interact meaningfully, it is important
that they understand each other enough to be able to shape each other’s behavior. This has
several implications. One of the most basic is that robot and human should have at least some
overlapping perceptual abilities (see chapters 5, 6, and 7). Otherwise, they can have little
idea of what the other is sensing and responding to. Similarity of perception requires more
than similarity of Sensors, however. Not all sensed stimuli are equally behaviorally relevant.
It is important that both human and robot find the same types of stimuli salient in similar
conditions. For this reason, Kismet is designed to have a set of perceptual biases based on
the human pre-attentive visual system. I have discussed this issue at length in chapter 6.

Similar visual attention Visual perception requires high bandwidth and is computation-
ally demanding. In the early stages of human vision, the entire visual field is processed in
parallel. Later computational steps are applied much more selectively, so that behaviorally
relevant parts of the visual field can be processed in greater detail. This mechanism of visual
attention is just as important for robots as it is for humans, from the same considerations
of resource allocation. The existence of visual attention is also key to satisfying the ex-
pectations of humans concerning what can and cannot be perceived visually. Recall that
chapter 6 presented the implementation of Kismet’s context-dependent attention system
that goes some way toward this.
Similar eye movements Kismet’s visual behaviors address both functional and social
issues. From a functional perspective, Kismet uses a set of human-like visual behaviors
that allow it to process the visual scene in a robust and efficient manner. These include
saccadic eye movements, smooth pursuit, target tracking, gaze fixation, and ballistic head-
eye orientation to target. We have also implemented two visual responses that very roughly
approximate the function of the VOR (however, the current implementation does not employ
a vestibular system), and the OKN. Due to human sensitivity to gaze, it is absolutely
imperative that Kismet’s eye movements look natural. Quite frankly, people find it disturbing
if they move in a non-human manner.
Kismet’s rich visual behavior can be conceptualized on those four levels presented in
chapter 9 (namely, the social level, the behavior level, the skills level, and the primitives
level). We have already argued how human-like visual behaviors have high communicative
value in different social contexts. Higher levels of motor control address these social issues
by coordinating the basic visual motor primitives (saccade, smooth pursuit, etc.) in a socially
appropriate manner. We describe these levels in detail below, starting at the lowest level (the
oculo-motor level) and progressing to the highest level where I discuss the social constraints
of animate vision.