Page 196 - Designing Sociable Robots

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Facial Animation and Expression 177

Figure 10.11
Kismet’s lip movements for expression. Alongside each of Kismet’s lip postures is a human sketch displaying an
analogous posture (Faigin, 1990). On the left, top to bottom, are: disgust, fear, and a frown. On the right, top to
bottom, are: surprise, anger, and a smile.

drawing that most closely resembled the robot’s expression. There was a short sequence
of questions to probe the similarity of the robot to the chosen line drawing. One question
asked how similar the robot’s expression was to the selected line drawing. Another question
asked the subject to list the labels of any other drawings they found to resemble the robot’s
expression and why. Finally, the subject could write any additional comments on the sheet.
Table 10.4 presents the compiled results.
The results are substantially above random chance (8 percent), with the expressions
corresponding to the primary emotions giving the strongest performance (70 percent and
above). Subjects could infer the intensity of expression for the robot’s expression of hap-
piness (a contented smile versus a big grin). They had decent performance (60 percent) in
matching Kismet’s stern expression (produced by zero arousal, zero valence, and strong
negative stance). The “sly grin” is a complex blend of positive valence, neutral arousal,
and closed stance. This expression gave the subjects the most trouble, but their matching
performance is still significantly above chance.
The misclassifications seem to arise from three sources. Certain subjects were confused
by Kismet’s lip mechanics. When the lips curve either up or down, there is a slight curvature
in the opposite direction at the lever arm insertion point. Most subjects ignored the bit of