Page 204 - Designing Sociable Robots

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11 Expressive Vocalization System

In the very first instance, he is learning that there is such a thing as language at all, that vocal sounds
are functional in character. He is learning that the articulatory resources with which he is endowed
can be put to the service of certain functions in his own life. For a child, using his voice is doing
something; it is a form of action, and one which soon develops its own patterns and its own significant
contexts.
—M.A.K. Halliday (1979, p. 10)

From Kismet’s inception, the synthetic nervous system has been designed with an eye
toward exploring the acquisition of meaningful communication. As Haliday argues, this
process is driven internally through motivations and externally through social engagement
with caregivers. Much of Kismet’s social interaction with its caregivers is based on vocal
exchanges when in face-to-face contact. At some point, these exchanges could be ritual-
ized into a variety of vocal games that could ultimately serve as learning episodes for the
acquisition of shared meanings. Towards this goal, this chapter focuses on Kismet’s vocal
production, expression, and delivery. The design issues are outlined below:

Production of novel utterances Given the goal of acquiring a proto-language, Kismet
must be able to experiment with its vocalizations to explore their effects on the caregiver’s
behavior. Hence the vocalization system must support this exploratory process. At the very
least the system should support the generation of short strings of phonemes, modulated by
pitch, duration, and energy. Human infants play with the same elements (and more) when
exploring their own vocalization abilities and the effect these vocalizations have on their
social world.
Expressive speech Kismet’s vocalizations should also convey the affective state of the
robot. This provides the caregiver with important information as to how to appropriately en-
gage Kismet. The robot could then use its emotive vocalizations to convey disapproval, frus-
tration,disappointment,attentiveness,orplayfulness.Asforhumaninfants,thisabilityisim-
portant for meaningful social exchanges with Kismet. It helps the caregiver to correctly read
the robot and to treat the robot as an intentional creature. This fosters richer and sustained
social interaction, and helps to maintain the person’s interest as well as that of the robot.
Lip synchronization For a compelling verbal exchange, it is also important for Kismet
to accompany its expressive speech with appropriate motor movements of the lips, jaw, and
face. The ability to lip synchronize with speech strengthens the perception of Kismet as a
social creature that expresses itself vocally. A disembodied voice would be a detriment to
the life-like quality of interaction that I and my colleagues have worked so hard to achieve
in many different ways. Furthermore, it is well-accepted that facial expressions (related
to affect) and facial displays (which serve a communication function) are important for
verbal communication. Synchronized movements of the face with voice both complement

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