The American philosopher Daniel Dennett believes that they work because, in order to understand and predict the behavior of the animate objects around them, people apply what he calls the intentional stance . Desires are the key to identifying with and understanding a character. We understand the actions of characters by inferring how their beliefs influence the ways they attempt to satisfy their desires. 2.1 Motivational Drives For a character to appear properly motivated it must continue to work towards satisfying its desires while gracefully handling unexpected situations. By biasing action selection towards behaviors that will satisfy the internal needs of the character, motivational drives provide a way to achieve goal-oriented behavior.
Most approaches agree on the general behavior of drives.
These desires can be attended to by the successful execution of attentive behaviors like eating, or by changes in external stimuli, such as temperature fluctuations or interactions with other characters. 2.2 Emotions Emotions bias action selection in much the same way as drives. For example, a character that is angry may be more prone to violent behavior than one who is happy. However, emotions also bias the quality of the character's motion. However varied they may be, these models tend to concede that, instead of increasing slowly over time as do drives, emotions typically exhibit a large impulse response followed by a gradual decay back down to a base state.