Page 115 - Designing Sociable Robots

breazeal-79017 book March 18, 2002 14:54

96 Chapter 7

Table 7.5
Table mapping [A, V, S] to classified affective intents. Praise biases the robot to be “happy,” prohibition biases it
to be “sad,” comfort evokes a “content, relaxed” state, and attention is “arousing.”

Category Arousal Valence Stance Typical Expression
Approval medium high high positive approach pleased
Prohibition low high negative withdraw sad
Comfort low medium positive neutral content
Attention high neutral aproach interest
Neutral neutral neutral neutral calm

arousing this percept is to the emotional system. Positive values correspond to a high arousal
stimulus whereas negative values correspond to a low arousal stimulus. The valence tag,
V , specifies how good or bad this percept is to the emotional system. Positive values
correspond to a pleasant stimulus whereas negative values correspond to an unpleasant
stimulus. The stance tag, S, specifies how approachable the percept is. Positive values
correspond to advance whereas negative values correspond to retreat. Because there are
potentially many different kinds of factors that modulate the robot’s affective state (e.g.,
behaviors, motivations, perceptions), this tagging process converts the myriad of factors
into a common currency that can be combined to determine the net affective state.
For Kismet, the [A, V, S] trio is the currency the emotion system uses to determine
which emotional response should be active. This occurs in two phases: First, all somatically
marked inputs are passed to the emotion elicitor stage. Each emotion process has an
elicitor associated with it that filters each of the incoming [A, V, S] contributions. Only
those contributions that satisfy the [A, V, S] criteria for that emotion process are allowed to
contribute to its activation. This filtering is done independently for each class of affective tag.
Given all these factors, each elicitor computes its net [A, V, S] contribution and activation
level, and passes them to the associated emotion process within the emotion arbitration
subsystem. In the second stage, the emotion processes within this subsystem compete for
activation based on their activation level. There is an emotion process for each of Ekman’s
six basic emotions (Ekman, 1992). The “Ekman six” encompass joy, anger, disgust,
fear, sorrow, and surprise. He posits that these six emotions are innate in humans, and
all others are acquired through experience.
Iftheactivationlevelofthewinningemotionprocesspassesabovethreshold,itisallowed
to influence the behavior system and the motor expression system. There are actually two
threshold levels, one for expression and one for behavior. The expression threshold is
lower than the behavior threshold; this allows the facial expression to lead the behavioral
response. This enhances the readability and interpretation of the robot’s behavior for the
human observer. For instance, given that the caregiver makes an attentional bid, the robot’s