The camera’s double-edged sword: a randomized experiment on how camera use affects perceived stress and expert-rated performance in online microteaching

Background Camera use in synchronous online teaching determines whether instructors are visually observable, yet experimental evidence on how this visibility affects instructors’ immediate stress and performance remains limited. This study compared perceived stress and expert-rated performance under camera-on and camera-off conditions during online microteaching among teacher-education students. Methods In a parallel-group randomized experiment, 70 participants were randomized to camera-on or camera-off conditions. Sixty-six attended the laboratory session and provided outcome data (camera-on n = 35; camera-off n = 31). Perceived stress was assessed immediately after teaching on a 5-point scale. Three experienced teacher educators rated teaching performance from the recordings using a prespecified rubric. Neuroticism and conscientiousness were examined in exploratory moderation analyses, and primary comparisons were supplemented with covariate-adjusted robustness models. Results Perceived stress was higher in the camera-on condition than in the camera-off condition ( M = 3.40 vs. 2.10, d = 1.67, p < 0.001). Expert-rated performance was also higher in the camera-on condition ( M = 90.67 vs. 86.55, d = 1.32, p < 0.001). Covariate-adjusted robustness models yielded similar estimates. Neuroticism showed a small positive association with perceived stress, whereas the exploratory analyses provided no evidence that neuroticism or conscientiousness moderated the camera-condition effects. Conclusions These findings suggest that the camera-on configuration operates as a double-edged situational cue, yielding higher perceived stress alongside more favorable evaluations. Notably, performance ratings may partly reflect visual information available to raters rather than purely enacted teaching behavior. Future research should examine whether these effects extend to more interactive teaching contexts and diverse participant populations. Trial registration This study was retrospectively registered at the Chinese Clinical Trial Registry (ChiCTR2600123389) on 26 April 2026. Chinese Clinical Trial Registry, ChiCTR2600123389; registered on 26 April 2026; retrospectively registered.