Evolutionary Entertainment with Intelligent Agents

A common limitation of conventional video games is that players quickly learn the positions and behavior of computer-controlled characters , which usually take the form of monsters. Software developers pre-program these characteristics so, after playing the game several times, the player comes to know exactly how and when the monsters will act. The game eventually becomes boring because the player need only execute a learned script to defeat the monsters and overcome all the hurdles he or she faces. This pattern has sparked increasing interest in using computational intelligence techniques to control the actions of computer characters, rather than relying on simple heuristics or rule-based systems. In particular, evolutionary computation and neural networks are being adapted to let software characters learn from their own experience, predict what a player might do next, and take appropriate action to meet their own challenges. In this way, a game can remain perpetually novel, posing new tests for the player each time he or she plays. In pursuit of this goal, game developers can combine evolutionary computation and neural networks to let software agents learn appropriate behaviors even in complex strategy games, without resorting to prepro-grammed features provided by software engineers a priori. The evolutionary process can even invent its own features for describing situations in a game and learn to weight those features and act based on patterns it recognizes. To place this capability in context, consider the following thought experiment. Suppose you sit down at a table to play a game with an opponent. You've never played a game of any type before. You face a two-dimensional board with eight squares on each side, with alternating colors, and, as Figure 1 shows, pieces occupy every other square. You're told the rules: The game takes place in turns, red moves first, and pieces move forward one square at a time, diagonally. Further, pieces that reach the back row become kings, a status that lets them move forward or backward one square at a time. Finally, when the possibility of jumping over an opponent's piece becomes available, you must take that jump move and remove the opponent's piece from play. What you aren't told is the object of the game. Instead, your opponent gives you the first move and responds in kind. After some number of moves, you're told that the game has ended and you're challenged to play again. Naturally, you'd like to …