38. A computer readable medium encoding computer readable instructions for controlling a synthetic character that is autonomous and interacts with others in a shared environment, such character having an associated mental state that changes over time at least in part as a function of said mental state, said mental state comprising a dynamic perceptual state that depends on said shared environment, said shared environment including the entities with which the character is interacting, and an action state defining actions to be taken by the character, that cause a processor to perform steps comprising: providing speech data corresponding to at least a part of an intended communication generated by the character; creating modified speech data by modifying, by an automatically determined amount, at least one of the pitch or duration of at least a portion of the speech data, such modification based at least in part on at least a portion of said mental state; and generating speech sounds associated with the character using the modified speech data wherein the mental state is determined at least in part by interaction of the character with others in a shared environment.
38. A computer readable medium encoding computer readable instructions for controlling a synthetic character that is autonomous and interacts with others in a shared environment, such character having an associated mental state that changes over time at least in part as a function of said mental state, said mental state comprising a dynamic perceptual state that depends on said shared environment, said shared environment including the entities with which the character is interacting, and an action state defining actions to be taken by the character, that cause a processor to perform steps comprising: providing speech data corresponding to at least a part of an intended communication generated by the character; creating modified speech data by modifying, by an automatically determined amount, at least one of the pitch or duration of at least a portion of the speech data, such modification based at least in part on at least a portion of said mental state; and generating speech sounds associated with the character using the modified speech data wherein the mental state is determined at least in part by interaction of the character with others in a shared environment. 39. The computer readable medium of claim 38 wherein said modification of pitch or duration is performed at least in part using the Synchronous Overlap and Add class of techniques.