A science teaching material video was made into a mosaic video. In the study, subjects watched both the teaching material video and the mosaic video. Subjects' pupil sizes were measured each time. The difference in relative mean pupil size between the teaching material video and the mosaic video is an index of the degree of interest. If the value is positive, the subject takes interest in part of the video. If the value is negative, the subject takes no interest in the part of the video.