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Social Amplification
Kismet is designed to make use of human social protocol for various purposes. One such purpose is to make life easier for its vision system. If a person is visible, but is too distant for their face to be imaged at adequate resolution, Kismet engages in a calling behavior to summon the person closer. People who come too close to the robot also cause difficulties for the cameras with narrow fields of view, since only a small part of a face may be visible. In this circumstance, a withdrawal response is invoked, where Kismet draws back physically from the person. This behavior, by itself, aids the cameras somewhat by increasing the distance between Kismet and the human. But the behavior can have a secondary and greater effect through social amplification -- for a human close to Kismet, a withdrawal response is a strong social cue to back away, since it is analogous to the human response to invasions of ``personal space.''
Similar kinds of behavior can be used to support the visual perception of objects. If an object is too close, Kismet can lean away from it; if it is too far away, Kismet can crane its neck towards it. Again, in a social context, such actions have power beyond their immediate physical consequences. A human, reading intent into the robot's actions, may amplify those actions. For example, neck-craning towards a toy may be interpreted as interest in that toy, resulting in the human bringing the toy closer to the robot. Another limitation of the visual system is how quickly it can track moving objects. If objects or people move at excessive speeds, Kismet has difficulty tracking them continuously. To bias people away from excessively boisterous behavior in their own movements or in the movement of objects they manipulate, Kismet shows irritation when its tracker is at the limits of its ability. These limits are either physical (the maximum rate at which the eyes and neck move), or computational (the maximum displacement per frame from the cameras over which a target is searched for).
Envelope Displays
Such regulatory mechanisms play roles in more complex social interactions, such as conversational turn-taking. Here control of gaze direction is important for regulating conversation rate. In general, people are likely to glance aside when they begin their turn, and make eye contact when they are prepared to relinquish their turn and await a response. People tend to raise their brows when listening or waiting for the other to speak. Blinks occur most frequently at the end of an utterance. These envelope displays and other cues allow Kismet to influence the flow of conversation to the advantage of its auditory processing. The visual-motor system can also be driven by the requirements of a nominally unrelated sensory modality, just as behaviors that seem completely orthogonal to vision (such as ear-wiggling during the call behavior to attract a person's attention) are nevertheless recruited for the purposes of regulation.
Other Regulatory Displays
Some regulatory displays also help protect the robot. Objects that suddenly appear close to the robot trigger a looming reflex, causing the robot to quickly withdraw and appear startled. If the event is repeated, the response quickly habituates and the robot simply appears annoyed, since its best strategy for ending these repetitions is to clearly signal that they are undesirable. Similarly, rapidly moving objects close to the robot are threatening and trigger an escape response. These mechanisms are all designed to elicit natural and intuitive responses from humans, without any special training. But even without these carefully crafted mechanisms, it is often clear to a human when Kismet's perception is failing, and what corrective action would help, because the robot's perception is reflected in behavior in a familiar way. Inferences made based on our human preconceptions are actually likely to work.
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