The Effect of Dynamic Facial Asymmetries on the Perceived Believability, Appeal, and Naturalness of Animated Agents

An animated agent’s believability, often defined as “the illusion of life,” has many facets, including the agent’s appearance, movements, and user interactions. Considering that human facial expressions are often not symmetrical, evaluating how facial expression asymmetries affect believability in animated agents would provide valuable insights for researchers and artists. Our research focused on facial movements and examined the impact of three dynamic facial asymmetries on users’ perception of the agent’s believability, appeal, and naturalness. Our research involved three studies: 1) a preliminary study in which we determined the maximum values to base asymmetry levels, 2) a study in which we identified what level of asymmetry yields the most perceived believability for each asymmetry location, and 3) a study in which we determined what effects different combinations of asymmetries have on perceived believability, appeal, and naturalness. The findings confirmed the effect of dynamic facial asymmetry on the agents’ perceived believability, appeal, and naturalness. Furthermore, our research suggests that including one or a combination of asymmetric eyebrow, mouth, or eyelid motions increases the agents’ perceived believability, appeal, and naturalness.