In this paper, we report a study on the use of Algorithm Visualizations (AV) in collaborative learning. Our previous results have confirmed the hypothesis that students' higher engagement has a positive effect on learning outcomes. Thus, we now analyze the students' collaborative learning process in order to find phenomena that explain the learning improvements. Based on the study of the recorded screens and audio during the learning, we show that the amount of collaboration and discussion increases during the learning sessions when the level of engagement increases. Furthermore, the groups that used visualizations on higher level of engagement, discussed the learned topic on different levels of abstraction whereas groups that used visualizations on lower levels of engagement tended to concentrate more on only one aspect of the topic. Therefore, we conclude that the level of engagement predicts, not only the learning performance, but also the amount of on-topic discussion in collaboration. Furthermore, we claim that the amount and quality of discussions explain the learning performance differences when students use visualizations in collaboration on different levels of engagement.