We investigated the effects of facial similarity between users and embodied agents under different experimental conditions. Sixty-four undergraduates interacted with two different embodied agents: in one case the agent was designed to look somewhat similar to the user, and in the other case the agent was designed to look dissimilar. We varied between subjects how helpful the agent was for a given task. Results showed that the facial similarity manipulation sometimes affected participants' responses, even though they did not consciously detect the similarity. Specifically, when the agent was helpful, facial similarity increased participantsi ratings of involvement. However, when exposed to unhelpful agents, male participants had negative responses to the similar-looking agent compared to the dissimilar one. These results suggest that using facially similar embodied agents has a potential large downside if that embodied agent is perceived to be unhelpful.

Abstract This paper presents an empirically tested theoretical framework to explain user engagement and end‐user satisfaction with interactive agents. Such a framework is not only important from a scientific point of view; application designers may find a set of dos and don'ts that help them create more satisfying embodied agents in different task domains and social settings. From a multidisciplinary perspective, we have conducted a series of experiments to verify underlying mechanisms in the processes of interacting and engaging with embodied agents in various task domains. Our results show that the most commonly held views are not always tenable; sometimes other factors provide better explanations for liking an embodied agent or end‐user satisfaction. For example, it is not realism but rather affordances and ethics that are key for understanding user responses, and a beautiful design is not always the most preferable. From our results, guidelines for designers and future research are reflected upon. Copyright © 2009 John Wiley & Sons, Ltd.

Human-like characters in the interface may evoke social responses in users, and literature suggests that realism is the most important factor herein. However, the effects of interface characters on the user are not well understood. We developed an integrative framework, called I-PEFiC, to explain ‘persona’ and realism effects on the user. We tested an important part of the model using an experimental design in which 140 middle school students were class-wise shown an informative virtual reality demonstration that incorporated either a realistic or an unrealistic (fantasy) interface character, or no character. Findings show, first, no persona effect on task performance. We discuss how user engagement might be related to persona effects. Second, designed realism of the interface character contributed to user engagement when controlled for various user perceptions. Moreover, perceived aesthetics and task-relevance further influenced user engagement. Third, user engagement and task performance combined better predicted satisfaction than either one of the factors alone. In sum, several appearance- and task-related factors contributed to user engagement and user satisfaction. Thus, realism is not all.