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practices of animation from Disney and other animators, and applied them on the
development of emotional expressions and idle behaviours for the EMYS robot. The
idle behaviour was adapted to our scenario to work in conjunction with the gaze
system. Facial expressions are used in our scenario for establishing turn-taking and
for revealing internal states like confusion, engagement, liking, etc.
The robot's non verbal behaviour also has a mood variable that can be either
positive or negative. Like in our previous scenario (Leite et al.
2008
), this variable
is mapped to a positive or negative posture.
Regarding the robot's verbal behaviour we defined a typology of speeches adapted
to the Risk game by separating utterances that human players vocalize in different
categories (Prada et al.
2011
). This categorization helped us in pinpointing the most
important behaviours in Risk but also a database of possible utterances. This database
contributed for the creation of a believable vocalization system, as the utterances in
this system were retrieved from real human social behaviour. In our scenario, a high
quality text to speech is used to vocalize these utterances.
7.4.3
Emotion or Appraisal System
After performing studies on the original Risk game, we were able to extract the
most relevant variables that influence human's appraisal. We achieved this by asking
participants to think out loud while they were playing Risk. These appraisal variables
evolve during the game and some of them are stored in the agent's memory for future
interactions. The chosen variables and how these variables are computed is in our
opinion quite scenario dependent. The ones we chose were based upon the results of
our studies and how we compute them by a simplification of each of these processes.
However, most of these variables might make sense in many other scenarios.
Our artificial opponent's emotion system is comprised by several appraisal vari-
ables. Variables such as
power, mood
and
concentration
influence the robot's gaze
system and idle behaviour.
Relevance
of an event influences our robot's dialogue
system. Also, when generating dialogue or choosing the next move to play, our arti-
ficial opponent takes into account relationship appraisal variables established towards
particular users. These variables are
familiarity
,
like/dislike
and
luck perception
.
7.4.4
Recognise, Greet and Remember Users
In our application we simplified the recognition process by making each user login
with their own private interface on the digital table. At that time the robot acknowl-
edges the presence and position of a user, greets that particular user, and updates the
history with him/her.
Some of the appraisal variables described in the subsection above evolve only
during the game, but some are stored in the agent's memory for future interactions.
