Page 64 - Designing Sociable Robots

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Designing Sociable Robots 45

because of its inherent saliency, such as a red ball may stand out from the background. Or
perhaps its quality has special behavioral significance for the robot, such as being a typical
indication of danger. See chapter 6 and the third CD-ROM demonstration titled “Directing
Kismet’s Attention” for more details.
The perceptual system The low-level features corresponding to the target stimuli of
the attention system are fed into the perceptual system. Here they are encapsulated into
behaviorally relevant percepts. To environmentally elicit processes in these systems, each
behavior and emotive response has an associated releaser. As conceptualized by Tinbergen
(1951) and Lorenz (1973), a releaser can be viewed as a collection of feature detectors that
are minimally necessary to identify a particular object or event of behavioral significance.
The releasers’ function is to ascertain if all environmental (perceptual) conditions are right
for the response to become active. High-level perceptions that influence emotive responses
are presented in chapter 8, and those that influence task-based behavior are presented in
chapter 9.

The motivation system The motivation system consists of the robot’s basic “drives” and
“emotions” (see chapter 8). The “drives” represent the basic “needs” of the robot and are
modeled as simple homeostatic regulation mechanisms (Carver & Scheier, 1998). When
the needs of the robot are being adequately met, the intensity level of each drive is within
a desired regime. As the intensity level moves farther away from the homeostatic regime,
the robot becomes more strongly motivated to engage in behaviors that restore that drive.
Hence, the drives largely establish the robot’s own agenda and play a significant role in
determining which behavior(s) the robot activates at any one time.
The “emotions” are modeled from a functional perspective. Based on simple appraisals of
a given stimulus, the robot evokes either positive emotive responses that serve to bring itself
closer to it, or negative emotive responses in order to withdraw from it (refer to the seventh
CD-ROM demonstration titled “Emotive Responses”). There is a distinct emotive response
for each class of eliciting conditions. Currently, six basic emotive responses are modeled
that give the robot synthetic analogs of anger, disgust, fear, joy, sorrow, and surprise (Ekman,
1992).Therearealsoarousal-basedresponsesthatcorrespondtointerest,calm,andboredom
that are modeled in a similar way. The expression of emotive responses promotes empathy
from the caregiver and plays an important role in regulating social interaction with the
human. (These expressions are viewable via the second CD-ROM demonstration titled
“Readable Expressions.”)
The behavior system The behavior system organizes the robot’s task-based behaviors
into a coherent structure. Each behavior is viewed as a self-interested, goal-directed entity
that competes with other behaviors to establish the current task. An arbitration mechanism