Embodied Conversational Agents (ECAs) can increase user engagement and involvement and can strengthen the effect of an intervention on health outcomes that is provided via an ECA. However, evidence regarding the effectiveness of ECAs on health outcomes is still limited. In this article, we report on a study that has the goal to identify the effect of a match between a health topic and the ECAs' appearance on ratings of personality characteristics, persuasiveness and intention to use. We report on an online experiment with three different ECAs and three different health topics, conducted among 732 older adults. We triangulated the quantitative results with qualitative insights from a focus group. The results reveal that older adults prefer an ECA that has an appearance matching a certain health topic, resulting in higher ratings on persuasiveness and intention to use. Personality characteristics should be measured embedded within a health topic, but are not rated higher because of a match. We furthermore provide guidelines for designing the content of the ECA.
Keywords: design guidelines; embodied conversational agent; health behavior change; persuasiveness.