Perceived Realism and Voice Naturalness of Virtual Humans: Structural Equation Modeling of Behavioral Intentions among Black American Adults

Virtual health assistants, digital characters designed to guide patients through healthcare interventions, offer scalable solutions, but their effectiveness may depend on user perceptions of realism. This study investigated how the visual fidelity and voice modality of virtual health assistants influence perceived realism, perceived voice naturalness, and intentions to screen for colorectal cancer among Black American adults aged 45–75. In a 2×4 factorial between-participants experiment (N=266), participants were randomized to virtual health assistants varying in visual fidelity and voice modality. Structural equation modeling revealed that voice naturalness had a strong positive effect on perceived realism, which in turn significantly predicted screening intentions. Visual fidelity also contributed directly to perceived realism, though to a lesser extent. These results suggest that enhancing voice naturalness in virtual health assistants may be a critical design priority for improving engagement and promoting preventive health behaviors in digital health interventions.