Page 133 - Designing Sociable Robots

breazeal-79017 book March 18, 2002 14:5

114 Chapter 8

expression of affect in Kismet’s face, posture, and voice are covered in chapters 10 and 11.
Adetaileddescriptionofhowthebehavioralresponsesareimplementedisgiveninchapter9.
Emotive Releasers

I begin this discussion with the input to the emotion system. The input originates from
the high-level perceptual system, where it is fed into an associated releaser process. Each
releaser can be thought of as a simple “cognitive” assessment that combines lower-level
perceptual features into behaviorally significant perceptual categories.
There are many different kinds of releasers defined for Kismet, each hand-crafted, and
each combining different contributions from a variety of factors. Each releaser is evaluated
with respect to the robot’s “well-being” and its goals. This evaluation is converted into an
activation level for that releaser. If the perceptual features and evaluation are such that the
activation level is above threshold (i.e., the conditions specified by that releaser hold), then
its output is passed to its corresponding behavior process in the behavior system. It is also
passed to the affective appraisal stage where it can influence the emotion system. There are
a number of factors that contribute to the assessment made by each releaser. They are as
follows:

• Drives The active drive provides important context for many releasers. In general, it
determines whether a given type of stimulus is either desired or undesired. For instance, if
the social-drive is active, then skin-toned stimuli are desirable, but colorful stimuli are
undesirable (even if they are of good quality). Hence, this motivational context plays an
important role in determining whether the emotional response will be one of incorporation
or rejection of a presented stimulus.
• Affective State The current affective state provides important context for certain re-
leasers. A good example is the soothing-speech releaser described in chapter 7. Given a
“soothing” classification from the affective intent recognizer, the soothing-speech re-
leaser only becomes active if Kismet is “distressed.” Otherwise, the neutral-speech
releaser is activated. This second stage of processing reduces the number of misclassifica-
tions between soothing speech versus neutral speech.
• Active Behavior(s) The behavioral state also plays an important role in disambiguating
certain perceptual conditions. For instance, a no-face perceptual condition could corre-
spond to several different possibilities. The robot could be engaged in a seek-people
behavior, in which case a skin-toned stimulus is a desired but absent stimulus. Initially
this would encourage exploration. Over time, however, this could contribute to an state of
deprivation due to a long-term loss. Alternatively, the robot could be engaged in an escape
behavior. In this case, no-face corresponds to successful escape, a rewarding circumstance.