Table 1.

Classification of interactivity in Plötzner et al. (1999), Kobayashi (2018), and this paper.

Explanation and teaching	Plötzner et al. (1999)	Kobayashi (2018)	This paper
Explaining to oneself	Level 1	–	Non-interactive
Explaining to an imaginary or anonymous student (e.g., creating a lecture video, providing written explanations)	Level 2	Non-interactive teaching	Indirect teaching
Explaining to a passive and anonymous student who just listens	Level 3	–	–
Explaining to a student of one’s acquaintance who responds in a constrained way; teaching a student face-to-face, without asking or answering questions	Level 4	Interactive teaching	Direct teaching
Teaching a student face-to-face, asking and answering questions	–	Interactive teaching	Direct teaching
Mutually explaining to each other	Level 5	–	–