The face system must be quite versatile as the manner in which these four functions are manifest changes dynamically with motivational state and environmental factors. However, people seem to be the most captivated by Kismet's emotive facial expressions. Consequently, we will focus on Kismet's expressive abilities here. When designing the expressive abilities of a robot face, it is important to consider both the believability and readability of the facial behavior. Believability refers to how life-like the behavior appears.
Readability refers to how well the observer can correctly interpret the intended expression.
Kismet's face is always in motion, which greatly enhances its life-like quality. Kismet's facial expressions are generated using an interpolation-based technique over a three dimensional space. The three dimensions correspond to arousal, valence, and stance. The current affective state occupies a single point in this space at a time. As the robot's affective state changes, this point moves about within this space.