Age-Adaptive Visual Appearance Design of In-Vehicle Agents: A Mixed Experiment in Driving and Non-Driving Contexts

With the development of intelligent cockpits and in-vehicle human–machine interaction, in-vehicle agents have gradually become an important interaction medium connecting users with vehicle systems. As the most direct external representation of an in-vehicle agent, visual appearance may influence users’ evaluations of trust, satisfaction, and visual attractiveness. However, existing studies have mainly focused on in-vehicle voice interaction, trust in automation, or anthropomorphic characteristics of agents, while the adaptation of different visual appearance stimuli to users of different ages and task contexts remains insufficiently explored. Therefore, this study investigates age-adaptive visual appearance design for in-vehicle agents. A 3 × 2 × 2 mixed experimental design was adopted, with visual appearance stimulus, age group, and gender as independent variables. Forty-eight participants completed interaction tasks in simulated driving and non-driving contexts and evaluated the agents in terms of trust, satisfaction, and visual attractiveness. The results indicated that, within the present sample and the selected representative stimuli, age-related differences were observed in users’ evaluations of in-vehicle agent visual appearances. In driving tasks, visual appearance stimulus and age showed significant interaction effects on trust and satisfaction. In both driving and non-driving tasks, visual appearance stimulus and age showed significant interaction effects on visual attractiveness. Younger users tended to give higher evaluations to the selected animal-like and abstract stimuli, whereas relatively older users showed higher acceptance of the selected anthropomorphic stimulus. Open-ended feedback further indicated that the selected animal-like appearance had a relatively high selection proportion in both driving and non-driving tasks, especially in non-driving contexts, where it showed stronger emotional appeal. These preliminary findings suggest that the visual appearance design of in-vehicle agents may benefit from considering users’ age differences and task contexts. However, because each appearance category was represented by only one visual stimulus, the findings should be interpreted as exploratory evidence based on specific representative stimuli rather than as general effects of abstract, animal-like, or anthropomorphic appearance categories. This study provides empirical references and preliminary design implications for user-centered visual design of in-vehicle agents in intelligent cockpits.