Emotional Agents for User Entertainment : Discussing the Underlying Assumptions

Emotional agents can play a very important role in all those computer applications where the user does not (only) want to perform a task, but (also) to he entertained or to have a more engaging experience than with traditional systems. In fact, it is commonly assumed that the agents' ability to process and display affective states, and to show emotional reactions, is crucial for causing a more enjoyable interaction between agent and user. This work proposes to analyze such assumption from a critical viewpoint, identifying several open issues that are worth debating in the community and studying through empirical methods. User interfaces are becoming more and more friendly, adaptive, and sensitive to the user's needs, preferences and wants. Along with this trend, computers are starting to comply with the user's wish to be entertained while or besides performing some "serious" task. For example, instructional software systems are being enhanced by lively anthropomorphic or animal-like tutors [7,15]; multimedia presentation systems might look more likeable if they present material through expressive animations [I]; PC desktops may be more exciting if populated by "virtual pets" that can interact with the user and with one another in interesting ways [5]. The issue of user's entertainment is to be "taken seriously", since it can deeply influence the effect of software applications, and even make the difference between a successful and an unsuccessful interface. I n fact, computer-based entertainment can not only be an interesting purpose in itself (as in the case of PC games, multi-user virtual environments, or software toys), but can also increase the user's satisfaction, boost her motivation to interact with an application (which, for example, is very important in the case of "edutainment"), help relieve the tensions that are usually related to the performance of difficult tasks, and give the opportunity to have a break from hard work. Such properties of entertainment come from its basically emotional nature and impact. * The author is currently supported by a scholarship from the Committee 1 2 (Information Science and Technology) of the National Research Council of Italy. She is indebted to Maria Miceli and Amedeo Cesta for their useful comments, and to Daniela Petrelli and Elisabeth Andre for suggesting some relevant references. Interfaces can be made more enjoyable by means of "believable agents" (also known as "lifelike computer characters", "synthetic agents", "virtual actors", and "animate characters"): these computational systems are built with the purpose of provoking in the user the "illusion of life" or, in other words, the impression of interacting with a "living" virtual being that has its own feelings, desires, and beliefs. A strong argument in favor of using believable agents in interfaces is that they make interacting with computers much easier and nicer, enable (especially naive) users to adopt communicative styles similar to those typical of human-human communication [I], and can increase the level of interactivity and socio-emotional engagement produced by traditional applications. There are also some arguments criticizing the usability of agents in interfaces: in fact, agents might compromise the user's feeling of control over the tasks being performed, or might generate in the user wrong expectations about their own capabilities [11,18]. Nevertheless, among the advocates of lifelike computer characters, it is also commonly believed that the agents' ability to process and display affective states, and to show emotional reactions, is crucial for improving the agents' believability, for eliciting emotions in the user, and consequently for causing a more entertaining interaction between agent and user [12,2]. Therefore, several research projects are aimed at realizing emotional agents (e.g. [4, 14,811. These agents are a promising direction of research on entertaining interfaces, but their realization and use seem to rely on assumptions that have not yet been made explicit and studied in great depth; this work proposes to outline and analyse them. In our view, such an analysis can be useful in two ways: on the one hand, it can help understand what are the main problems to address when realizing emotional agents; on the -other hand, it can drive the empirical validation of the most common hypotheses regarding the relationships between entertainment, emotions, and believability, in order to build more effective agents. Emotional agents are usually inspired by characters realized in traditional media like drama, cinema, cartoons, and seem to be founded on the following hypotheses: Hypothesis 1: entertainment is a function of the character's ability to cause the "illusion of life" (believability); Hypothesis 2: entertainment is a function of the character's ability to induce emotions. These hypotheses, although difficult to verify empirically, are hardly questionable; they can actually be considered as basic assumptions. In fact, we have many examples of their validity from traditional media: the more believable a character is, the more likeable it is, and the emotions it can induce greatly contribute to the spectator's entertainment. This notion of believability is different from the perceived "credibility" of computer applications, which refers to the delivery of trustworthy information. [19] In our view, the assumptions above are motivated by more specific and usually implicit hypotheses, that generally drive the actual realization of emotional agents: Hypothesis 3: believability crucially depends on the agent's ability to show emotional reactions; Hypothesis 4: believability also depends on the manifestationof a marked personality, which in its turn is based on an individual style of emotional behaviors; Hypothesis 5: the user's emotional responses to an agent depend on the latter's emotional behavior; Hypothesis 6: the agent's ability to show emotional reactions depends on its ability to represent and process emotional states. Such hypotheses appear to be related to each other according to an instrumental hierarchy, as shown in figure 1: from bottom up, agent designers usually assume that the ability to represent and process affective states, which can be brought about by events affecting an agent's goals, preferences, or values, enables the agent to display emotional reactions; these in turn are deemed essential for enhancing the agent's believability, for characterizing its unique personality, which also contributes to believability, and for arousing emotions in the observer, possibly through an empathic process; finally, the agent's believability, and its ability to induce affective reactions in the user, are expected to cause the latter to be entertained. The user's entertainment can be an end in itself, or it can be functional to other affective states, such as satisfaction, ease, motivation, and the like, that can influence the effectiveness of several kinds of computer applications.