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possible to simulate place illusion by playing a computer game inside an immersive
or pervasive system.
Plausibility illusion relates to the illusion that what is happening is really happen-
ing, even though the user knows it is not. It is also described as the extent in which
the system can produce events that relate to the participant, and to the credibility
of the scenario being depicted in comparison with user's expectations. In order to
achieve Plausibility illusion, credible scenarios with very little room for error and
with plausible interactions between participants and entities in the environment are
required. In our case, the focus is in modelling socially believable artificial opponents
for board games, where the virtual environment is mainly comprised by a virtual op-
ponent. Here, plausibility illusion directly relates to definitions of social presence
whereas seen above, can be shortly described as “the sense of being together with
another”. Slater also argues (Slater
2009
), that plausibility illusion (social presence,
in our case) is a more fruitful and challenging research area than place illusion or
telepresence.
Contributing Factors to Social Presence
Social presence can be used to measure
the individual's perception of a particular interactive media, be it a virtual reality
environment (Heeter
1992
; Slater
2009
) or the interaction with a social robot (Scher-
merhorn et al.
2008
). Properties of the medium, context of interaction and individual
differences will change the way we experience social presence, this presence can be
superficial or strong enough to elicit powerful emotional reactions, such as crying at
a movie screening or smiling at a computer character. Several authors have discussed
which factors influence social presence, but none of them has focused in artificial
opponents before. In the remaining of this subsection we gather the factors that we
conceptualise to be the most important for creating a board game artificial opponent.
Interactivity
Interactivity is referred by most authors as the primary cause of pres-
ence. If users cannot interact with an artificial agent, they usually do not consider
it as a social entity. There are different modes of interacting with a virtual agent,
but in terms of social presence, face-to-face interaction is still considered the gold
standard in communication, against which all platforms are compared (Adalgeirs-
son and Breazeal
2010
). Social presence is assumed to be highest when two people
are within reach of each other interacting on a task (Biocca et al.
2001b
). As such,
virtual agents that do not use the rich set of social behaviours and cues involved in
face-to-face interaction are assumed to support less social presence. One reason why
face-to-face interaction is preferred is that a lot of familiar information is encoded
in the non-verbal cues that are being exchanged.
Face-to-face interaction is generally accompanied with verbal communication.
Machines are still quite limited in understanding the human counterpart in this re-
spect, both in terms of speech recognition and dialogue systems. However, there are
already some successful cases of virtual agents that are able to verbally interact with
humans in very contextualized scenarios (Anderson
2008
). The output of such sys-
tems is generally implemented by using pre-recorded utterances or by text-to-speech
systems. Voices with higher audio realism and fidelity increase the illusion of inter-
action with a social entity (Lombard and Ditton
1997
). High quality text to speech
