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156 Chapter 9

To scale the performance to adult human performance, however, the goal of a 250 ms delay
between speaking turns should be achieved.

9.8 Summary

Drawing strong inspiration from ethology, the behavior system arbitrates among competing
behaviors to address issues of relevance, coherency, flexibility, robustness, persistence, and
opportunism. This enables Kismet to behave in a complex, dynamic world. To socially en-
gage a human, however, its behavior must address issues of believability—such as conveying
intentionality, promoting empathy, being expressive, and displaying enough variability to
appear unscripted while remaining consistent. To accomplish this, a wide assortment of
proto-social, infant-like responses have been implemented. These responses encourage the
human caregiver to treat the robot as a young, socially aware creature. Particular attention
has been paid to those behaviors that allow the robot to actively engage a human, to call to
people if they are too far away, and to carry out proto-dialogues with them when they are
nearby. The robot employs turn-taking cues that humans use to entrain to the robot. As a re-
sult, the proto-dialogues become smoother over time. The general dynamics of the exchange
share structural similarity with those of three-month-old infants with their caregivers. All
five phases (initiation, mutual regard, greeting, play dialogue, and disengagement) can be
observed.
Kismet’smotorbehaviorisconceptualized,modeled,andimplementedonmultiplelevels.
Each level is a layer of abstraction with distinct timing, sensing, and interaction charac-
teristics. Each layer is implemented with a distinct set of mechanisms that address these
factors. The motor skills system coordinates the primitives of each specialized system for
facial animation, body posture, expressive vocalization, and oculo-motor control. I describe
each of these specialized motor systems in detail in the following chapters.