Artificial intelligence researchers attempting to create engaging, apparently living creatures may find important insight in the work of artists who have explored the idea of believable character. In particular, appropriately timed and clearly expressed emotion is a central requirement for believable characters. We discuss these ideas and suggest how they may apply to believable interactive characters, which we call "believable agents." This work was supported in part by Fujitsu Laboratories and Mitsubishi Electric Research Laboratories. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of any other parties.

vii List of Figures xii Chapter 1.