Recent years have witnessed a growing interest in employing animated agents for tasks that are typically performed by humans. They serve as communicative partners in a variety of applications, such as tutoring systems, sales, or entertainment. This paper first discusses design principles for animated agents to enhance their effectiveness as tutors, sales persons, or actors, among other roles. It is argued that agents should support their perception as social actors by displaying human-like social cues such as affect and gestures. An architecture for emotion-based agents will be described and a simplified version of the model will be illustrated by two interaction scenarios that feature cartoon-style characters and can be run in a web browser. The second focus of this paper is an empirical evaluation of the effect of an affective agent on users' emotional state which is derived from physiological signals of the user. Our findings suggest that an agent with affective behavior may significantly decrease user frustration.

This paper highlights some of our recent research efforts in designing and evaluating life-like characters that are capable of entertaining affective and social communication with human users. The key novelty of our approach is the use of human physiological information: first, as a method to evaluate the effect of life-like character behavior on a moment-to-moment basis, and second, as an input modality for a new generation of interface agents that we call 'physiologically perceptive' life-like characters. By exploiting the stream of primarily involuntary human responses, such as autonomic nervous system activity or eye movements, those characters are expected to respond to users' affective and social needs in a truly sensitive, and hence effective, friendly, and beneficial way.