Abstract:

With the growing popularity of online video learning, the question of how to improve the effectiveness of online learning has received increasing attention from researchers. Teachers play important roles in instructional videos, and their social cues, such as facial expressions, eye gaze, and gestures, can affect video learning performance. Among them, facial expression (i.e., positive, negative, neutral) is an important nonverbal cue for teachers. It is one of the boundary conditions in video learning where the teachers' presence affects the learning effect, which can affect the learning performance and the students' subjective experience by influencing the students' emotions compared to cues such as eye gaze and gesture. However, there are few studies on the effects of real teachers' facial expressions on video learning, and there are inconsistencies among the findings, so there is an urgent need to review and summarize the mechanisms by which teachers' facial expressions affect video learning and to provide new directions for future research. This paper focuses on the research issue of the effect of real teachers' facial expressions on learning in video learning, summarizes 17 previous empirical studies, and attempts to analyze the results of these studies.

Based on the median effect size, this review indicates that, for the learning performance, teachers' positive facial expressions can promote the retention (d _retention = 0.53) and transfer (d _transfer = 0.41) test. Moreover, positive facial expressions can improve performance on the delayed joint test (retention test and transfer test) more than on the immediate joint test. For the students' attention, positive teacher facial expressions have a small effect on the fixation time on learning content (d_{gaze time on slide} = 0.26) and the teachers' face (d _{gaze time on teachers' face} = 0.30). For the subjective experience, teachers' positive facial expressions can evoke students' positive emotions (d _{positive emotions} = 0.55), arousal (d _arousal = 0.84), motivation (d _motivation = 0.90), and decrease negative emotions (d _{negative emotions} = -0.52). However, teachers' positive facial expressions have a weaker effect on reducing the cognitive load (d _{cognitive load} = -0.17) and improving parasocial interaction (d _{parasocial interaction} = 0.23).

Based on the existing theories and the results of empirical studies, this review proposes a mechanism by which the facial expressions of real teachers affect video learning. Teachers' facial expressions can influence learning performance through three paths: cognitive, emotional, and social perception. Specifically, in the cognitive path, cognitive load theory (CLT) suggests that teachers' facial expressions distract students' attention from the learning content and increase students' cognitive load. However, according to the results of this review, although teachers' facial expressions increase attention to the teachers' faces, they do not increase cognitive load but rather encourage students to have the same emotions as the teacher, which in turn positively affects learning performance by increasing arousal and motivation. At the same time, facial expressions can also increase attention to the learning content, which in turn encourages students to increase their mental effort and have a positive learning performance. In the emotional path, in line with the cognitive-affective-social theory of learning in digital environments (CASTLE) and emotional contagion theory (ECT), the teacher's facial expressions, when recognized by students, produce the same emotions as those of the teacher, increasing arousal and motivation, and ultimately improving learning performance. In the social perception path, facial expression as a social cue for the teacher can facilitate the establishment of the student's cognitive schema, which produces a higher level of parasocial interaction, which in turn has an impact on learning performance, consistent with the para-social interaction theory (PSIT).

In conclusion, we suggest that teachers in instructional videos use positive facial expressions to help students better understand the learning content, focus their attention, evoke positive emotions and motivation, and enhance the interaction between teachers and students. Further research is required to elucidate the role of teachers' facial expressions in video learning, particularly with regard to experimental design, moderating variables, and underlying mechanisms.

Key words: facial expressions, teacher, video learning, multimedia learning