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Facial Animation and Expression 183

could be improved. They should be able to elevate at both corners of the brow, as opposed
to the arc of the current implementation. This would allow us to more accurately portray
the brow movements for fear and sorrow. Kismet’s mechanics attempt to approximate this,
but the movement could be strengthened. The insertion point of the motor lever arm to the
lips needs to be improved, or at least masked from plain view. Several subjects confused
the additional curve at the ends for other lip shapes.
In this chapter, I have only evaluated the readability of Kismet’s facial expressions. The
evaluation of Kismet’s facial displays will be addressed in chapter 12 and chapter 13, when
I discuss social interactions between human subjects and Kismet.
As a longer term extension, Kismet should be able to exert “voluntary” control over its
facialexpressionsandbeabletolearnnewfacialdisplays.Ihaveastronginterestinexploring
facial imitation in the context of imitative games. Certain forms of facial imitation appear
very early in human infants (Meltzoff & Moore, 1977). Meltzoff posits that imitation is an
important discovery procedure for learning about and understanding people. It may even
play a role in the acquisition of a theory of mind. For adult-level human social intelligence,
the question of how a robot could have a genuine theory of mind will need to be addressed.

10.7 Summary

A framework to control the facial movements of Kismet has been developed. The ex-
pressions and displays are generated in real-time and serve four facial functions. The lip
synchronization and facial emphasis subsystem is responsible for moving the lips and face
to accompany expressive speech. The emotive facial expression subsystem is responsible
for computing an appropriate emotive display. The facial display and behavior subsystem
produces facial movements that serve communicative functions (such as regulating turn
taking) as well as producing the facial component of behavioral responses. With so many
facial functions competing for the face actuators, a dynamic prioritizing scheme was de-
veloped. This system addresses the issues of blending as well as sequencing the concurrent
requests made by each of the face subsystems. The overall face control system produces
facial movements that are timely, coherent, intuitive and appropriate. It is organized in a
principled manner so that incremental improvements and additions can be made. An intrigu-
ing extension is to learn new facial behaviors through imitative games with the caregiver,
as well as to learn their social significance.