Page 87 - Socially Intelligent Agents Creating Relationships with Computers and Robots

70 Socially Intelligent Agents

to engage them in more interesting and long-lasting interactions; and (b) a clear
causal pattern for emotion elicitation was necessary for people to attribute in-
tentionality to the robot and to “understand” its displays. We turned to psy-
chology as a source of inspiration for more principled models of emotion to
design Feelix. However, we limited our model in two important ways. First,
expression (and its recognition) was restricted to the face, excluding other el-
ements that convey important emotion-related information such as speech or
body posture. Since we wanted Feelix’s emotions to be clearly recognizable,
we opted for a category approach rather than for a componential (dimensional)
one, as one of the main criteria used to define emotions as basic is their hav-
ing distinctive prototypical facial expressions. Second, exploiting the potential
that robots offer for physical manipulation—a very primary and natural form of
interaction—we restricted interaction with Feelix to tactile stimulation, rather
than to other sensory modalities that do not involve physical contact.
What could a very simple robot embodying these ideas tell us about emo-
tional expression and interaction? To answer this question, we performed emo-
tion recognition tests and observed people spontaneously playing with Feelix.

2. Feelix
Due to space limitations, we give below a very general description of the
robot and its emotion model, and refer the reader to [3] for technical details.

2.1 The Robot

Feelix is a 70cm-tall “humanoid” robot (Figure 8.1) built from commercial
LEGO Mindstorms robotic construction kits. Feelix expresses emotions by
means of its face. To interact with the robot, people sit or stand in front of it.
Since we wanted the interaction to be as natural as possible, the feet seemed the
best location for tactile stimulation, as they are protruding and easy to touch;
we thus attached a binary touch sensor underneath each foot.
Feelix’s face has four degrees of freedom (DoF) controlled by five motors,
and makes different emotional expressions by means of two eyebrows (1 DoF)
and two lips (3 DoF). The robot is controlled on-board by two LEGO Mind-
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storms RCX computers , which communicate via infrared messages.
2.2 Emotion Model

Feelix can display the subset of basic expressions proposed by Ekman in
[4], with the exception of disgust—i.e. anger, fear, happiness, sadness, and
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surprise, plus a neutral face . Although it is possible to combine two expres-
sions in Feelix’s face, the robot has only been tested using a winner-take-all