Straighten your back, open your arms! Effects of instructor's body postures in educational videos on students' interest and motivation

Background: Research on on-screen instructor videos in education highlighted the role of embodied social cues for students' interest and motivation. As essential components of nonverbal communication variations of instructors' body postures may enhance teaching and stimulate learning by affecting students' perception and attitudes. Aims: We investigate how an instructor's posture influence students' perceptions of and their attitudes towards an instructor in a video, as well as their interest and motivation regarding the topic. Sample: University students participated online in a pilot (N = 194), a complementary (audio track-comparison; N = 53), and a preregistered (N = 434) experiment. Methods: Participants were randomly assigned to watch one of four videos in which the instructor's posture was varied regarding verticality (upright vs. slumped) and horizontality (open vs. closed). We assessed students' perceptions of the instructor's enthusiasm, agency, and communion, liking and respect for the instructor, situational interest and motivation. Results: While perceived enthusiasm, agency, communion, and students' liking were affected by the vertical and the horizontal dimension, students' respect was only influenced by the horizontal dimension. Regarding situational interest and motivation, we found indirect-only mediation effects of both posture dimensions mediated through perceived enthusiasm. Further mediation analyses indicated that the vertical dimension affected respect indirectly and the horizontal dimension affected liking, both mediated through perceptions of agency and communion. Conclusions: Our study demonstrates that instructor's body postures as embodied social cues in educational videos affect students' perceptions of and attitudes towards the instructor, which in turn, shape students' interest and motivation.