Page 249 - Socially Intelligent Agents Creating Relationships with Computers and Robots

232 Socially Intelligent Agents

through a game’s story. The resulting collection of narrative paths is structured
so that each path provides the user with an interesting narrative experience and
ensures that the user’s expectations regarding narrative content are met. This
approach, of course, limits the number and type of stories that can be told inside
a single game.
In our work on interactive narrative in the Liquid Narrative research group
at North Carolina State University, our approach is to provide a mechanism by
which the narrative structure of a game is generated at execution time rather
than at design time, customized to user preferences and other contextual factors.
The programs that we use to create storylines build models of the story plots that
contain a rich causal structure – all causal relationships between actions in the
story are specifically marked by special annotations. We put the annotations to
good use during gameplay every time that a user attempts to perform an action.
As a user attempts to change the state of the world (e.g., by opening a door,
picking up or dropping an artifact), a detailed internal model of that action is
checked against the causal annotations present in the story. As I describe in
more detail below, if the successful completion of the user’s action poses a threat
to any of the story structure, the system responds to ensure that the actions of
the user are integrated as best as possible into the story context.
It is the interactive nature of a computer game that contributes most strongly
to the unique sense of agency that gamers experience in the narratives that the
game environment supports. But the role of the gamer in a typical computer
game is not one of director, but rather of lead character. She does not enter the
game world omniscient and omnipotent, but experiences the story that unfolds
around her character simultaneously through the eyes of an audience member,
the eyes of a performer and through the eyes of her character itself. To uphold
her portion of the co-operative contract, she must act well her part, given her
limited perceptions and capability to change the game environment.
Consequently, the system creating the storyline behind the scenes must bear
most of the responsibility for maintaining the work product of the collaboration,
i.e., a coherent narrative experience. To do this, it must plan out ahead of time
an interesting path through the space of plot lines that might unfold within the
game’s storyworld. In addition, the game itself must keep constant watch over
the story currently unfolding, lest the user, either by ignorance, accident or
maliciousness, deviate from the charted course.
Fortunately, all aspects of a user’s activity with the game system, from the
graphical rendering of the world to the execution of the simplest of user actions,
are controlled (well at least, they’re controllable). It is the mediated nature of
the interaction between player and game environment that provides us with the
hook needed to make the game system co-operative in a Gricean sense. That
is, to provide the user with a sense of agency while still directing the flow of a
story around the user’s (possibly unpredicted) actions.