Visualizing timeline-anchored comments enhanced social presence and information searching in video-based learning

Numerous learners watch knowledgeable videos with comments or annotations anchored to the video timeline. These comments are learners' discussions with abundant informational and social content along with video timelines, but the content is usually fragmented and scattered. To extract, organize, and highlight useful information from the discussion, we adopted text mining approaches and designed an interactive visualization tool in the lecture interface for learners, including the following components along with the video timeline: (1) the relevance of comments to the lecture, (2) the comment topics throughout the lecture, and (3) the difficulty level perceived by learners. We conducted a lab experiment with 24 students to examine the effects of the visualization tool on the learning process and outcomes. We found that learners perceived a significantly higher social presence and performed better in open-book quizzes, searching tasks, and summarizing lectures using the visualization tool. This suggests that the visualization of timeline-anchored commenting potentially facilitates learners' participation in discussions and contributions to the learning community.