This book summarizes the results of a series of experiments conducted to examine the role, effectiveness, and related factors of “underlining behavior” in text-based learning situations. The studies investigated the effects of various factors, including the timing of recall tasks, the length of reading time, the difficulty level of learning materials, and individual learner differences such as reading comprehension ability and study habits. The results indicated that the effectiveness of a learning behavior is determined by the combination of factors such as study time and the difficulty of the materials. It was therefore suggested that, when examining the role of learning behaviors, considering them in relation to these factors clarifies their effectiveness as learning strategies and can help support learners’ activities.