Page 129 - Designing Sociable Robots

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110 Chapter 8

from itself. As time passes, this drive approaches the “exhausted” end of the spectrum.
Once the intensity level exceeds a certain threshold, it is time for the robot to “sleep.”
While the robot sleeps, all drives return to their homeostatic regimes. After this, the robot
awakens.
Drives and Affect

The drives spread activation energy to the emotion processes. In this manner, the robot’s
ability to satisfy its drives and remain in a state of “well-being” is reflected by its affective
state. When in the homeostatic regime, a drive spreads activation to those processes
characterized by positive valence and balanced arousal. This corresponds to a “contented”
affective state. When in the under-stimulated regime, a drive spreads activation to those
processes characterized by negative valence and low arousal. This corresponds to a “bored”
affective state that can eventually build to “sorrow.” When in the overwhelmed regime, a
drive spreads activation to those processes characterized by negative valence and high
arousal. This corresponds to an affective state of “distress.”
The emotion system influences the robot’s facial expression. The caregiver can read the
robot’s facial expression to interpret whether the robot is “distressed” or “content,” and can
adjust his/her interactions with the robot accordingly. The caregiver accomplishes this by
adjustingeitherthetype(socialversusnon-social)and/orthequality(lowintensity,moderate
intensity, or high intensity) of the stimulus presented to Kismet. These emotive cues are
critical for helping the human work with the robot to establish and maintain a suitable
interaction where the robot’s drives are satisfied, where it is sufficiently challenged, yet
where it is largely competent in the exchange.
In chapter 9, I present a detailed example of how the robot’s drives influence behavior
arbitration. In this way, the drives motivate which behavior the robot performs to bring
itself into contact with needed stimuli.

8.3 The Emotion System

Theorganizationandoperationoftheemotionsystemisstronglyinspiredbyvarioustheories
of emotions in humans. It is designed to be a flexible system that mediates between both
environmental and internal stimulation to elicit an adaptive behavioral response that serves
either social or self-maintenance functions (Breazeal, 2001a). The emotions are triggered
by various events that are evaluated as being of significance to the “well-being” of the
robot. Once triggered, each emotion serves a particular set of functions to establish a
desired relation between the robot and its environment. They motivate the robot to come
into contact with things that promote its “well-being” and to avoid those that do not.