The creators of interactive fiction have devised fun and interesting ways for computers and people to write interactively, together. Before there was literary hypertext, there were works that called on the reader to type a response or a command to the main character, continuing the text. These include the computer psychiatrist Eliza, the adventure game Zork, and an electronic novel, Mindwheel, written by Poet Laureate Robert Pinsky. The reader was called upon to do writing in these works, taking on the role of an "interactor."
Although enjoyable, occasionally artful, and even useful for educational purposes (such as language learning), the possible interactions were still quite limited. These works allow participation, but do not live up to the ideal of human/computer collaboration, or co-authorship. For the most part, they force the human participant into a particular role -- a patient in therapy or a treasure-collecting adventurer, for instance. This makes the interactor more of a theatrical or gaming "player." This role may be enjoyable, but is not the same role as "co-author."
By making improvements and reaching toward the goal of co-authorship, a work could be created which would allow broad creative freedom for the human interactor, who would write in concert with a provocative computer co-author. Such a system would have profound literary possibilities. Discussion of two of my projects illustrates ways to close in on interactive fiction's co-authorial grail.
In a project at the MIT Media Lab, EddieEdit, second and third graders conversed with a virtual kid editor by typing. Eddie the Editor asked story planning questions of the children before they started the main writing process, then discussed revision with them after they wrote a story unaided. This was a "human-heavy" interaction in which the computer was limited to a prompting and supporting role. EddieEdit demonstrated that a computer can fruitfully take such a role. Furthermore, the goal-oriented conversation in this system suggests a format for other types of textual interactive fiction.
My more recent work of interactive fiction for an adult readership, Winchester's Nightmare: A Novel Machine, uses a modified adventure game interface. In Winchester's Nightmare the text is continuous, instead of being punctuated by command prompts that differentiate the interactor's input from the computer's contribution. The experience is a "computer-heavy" interaction (the interactor is limited to completing a sentence every few lines) in which the interactor makes the decisions for the main character. Winchester's Nightmare provides an experience more aimed at literary reading and writing, and not as dominated by game-playing and puzzle-solving modes of thought. The interactor is not cast directly into the role of that character by being addressed in the second person, as is usually the case in adventure games. The redesign of the interface, informed by improvisational theater and conversational structure, made the experience more symmetrical, with the human contribution becoming more like that of the computer narrator. As a result, the nature of the interaction moves a few steps closer to co-authorship.