Page 187 - Designing Sociable Robots

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168 Chapter 10

Open stance
Low
fear arousal

accepting
Negative
valence
tired

unhappy

content
surprise

Positive
valence
disgust

stern
High
arousal
anger Closed stance
Figure 10.5
This diagram illustrates where the basis postures are located in affect space.

upward chin. Low arousal corresponds to a slouching posture where the neck lean and
head tilt are lowered. The posture remains neutral over the valence dimension. An open
stance corresponds to a forward lean movement, which suggests strong interest toward the
stimuli the robot is leaning toward. A closed stance corresponds to withdraw, reminiscent
of shrinking away from whatever the robot is looking at. In contrast to the facial expres-
sions (which are continually expressed), the affective postures are only expressed when
the corresponding emotion process has sufficiently strong activity. When expressed, the
posture is held for a minimum period of time so that the observer can read it, and then it
is released. The facial expression, of course, remains active. The posture is presented for
strong conveyance of a particular affective state.
The remaining three facial prototypes are used to strongly distinguish the expressions for
disgust, anger, and fear. Recall that four of the six primary emotions are characterized by
negative valence. Whereas the primary six basis postures (presented above) can generate
a range of negative expressions from distress to sadness, the expressions for intense anger
(rage), intense fear (terror), and intense disgust have some uniquely distinguishing features.
For instance, the prototype for disgust, P disgust , is unique in its asymmetry (typical of