Effect of nonverbal behaviors and speech characteristics of online medical ECAs on patients’ satisfaction: The mediating roles of empathy and trust

Objective Embodied conversational agents (ECAs) play a crucial role in digital healthcare. While existing studies have examined the effect of ECAs’ appearances and nonverbal behaviors on acceptance, the mechanism by which nonverbal behaviors and speech characteristics jointly influence patients’ satisfaction remains unclear. This study explores the impact of medical ECAs’ nonverbal behaviors and speech characteristics on patients’ perceived empathy, trust, and satisfaction. Methods This study adopted a mixed factorial experimental design. Independent variables included nonverbal behaviors (facial expressions: smiling/painful; body postures: open/closed) and verbal behaviors (speech rate and pitch: low/medium/high). Dependent variables included perceived empathy, trust, and satisfaction. Speech rate served as a between-subjects variable and pitch as a within-subjects variable. 75 participants were recruited to watch and interact with the 12 pre-recorded ECA videos presented in a random order. Perceived empathy, trust and satisfaction were measured. Results Body postures significantly affected satisfaction (p< .001), while facial expressions showed no significant impact (p=.302). Speech rate significantly influenced satisfaction (p=.034), with low rate yielding higher satisfaction than high rate (p= .044); pitch showed no significant main effect (p=.295). Trust fully mediated the relationship between nonverbal behaviors and satisfaction, while empathy and trust serially mediated this effect. Trust partially mediated speech characteristics’ effect on satisfaction. The combination of painful expression, open posture, low speech rate, and high pitch yielded significantly higher satisfaction than other conditions (p< .001). Conclusions Open body postures and low speech rate directly enhanced patients’ satisfaction. Trust mediated the effects of both nonverbal behaviors and speech characteristics on satisfaction. The optimal combination of open postures, painful expressions, high pitch, and low speech rate most effectively improved patient satisfaction. These findings provides empirical evidence for multimodal medical ECA design and enhancing digital health service experience.