- For a bell curve as a distribution of dice, see probabilities.
The bell curve of experiences is a principle in role-playing game theory that says every role-playing game must permit a range of possible experiences for any group and that, as a corollary, this range of experiences is distributed like a bell curve. Every experience that a player will have playing a game is a point under the game's bell curve of experiences. Some groups will have a negative ("un-fun") experience of a game, but this does not necessarily mean that the group did anything wrong when playing the game; negative experiences are valid points under the bell curve of experiences.
The bell curve of experiences exists because role-playing is both a social and creative activity that requires significant input from real people to be enjoyable, and the resulting experience can be affected by numerous factors both in and out of the game. A specific group playing a specific game may still have very different experiences at different times, but these experiences all fall under the bell curve.
The range of experiences is assumed to be a bell curve because most experiences of a game are expected to be in the middle of the curve, although this is hard to test because of the subjective nature of experience and the number of experiences that must take place. The most negative experiences, as well as the most positive experiences, are assumed to be far less common.
As a principle of RPG theory, the bell curve can be used by designers, playtesters and reviewers of games.
- For designers, understanding that a game will produce a bell curve of experiences means that the focus should not be to create a uniform experience for all players. Designers may seek to minimize negative experiences, enhance positive experiences, or simply to shift the entire bell curve to the positive end of the spectrum. Marketing can play a role in addressing the bell curve by attracting players whose experiences will be more positive (e.g. more appropriate to the design intentions of the game) while warning away players whose experiences are likely to be more negative.
- For playtesters, the bell curve demonstrates that a single playtest of a game can't reveal every potential experience permitted by a game. Although a single playtest is likely to fall in the middle of the curve, it is also possible that single playtests could be outliers (either exceptionally positive or exceptionally negative). More playtests give a better picture of the shape and position of the bell curve.
- For reviewers, the bell curve demonstrates that a single play of a game is not necessarily enough to understand every experience under the curve. As with playtesting, more games give a better picture of the shape and position of the bell curve.
The bell curve of experiences was proposed by Vincent Baker.