Algorithm Visualization Environments: Degree of interactivity as an influence on student-learning

Nowadays, online learning environments have become very popular for teaching algorithms. To improve the learning process these environments often include various visualizations of the algorithms. Because of the abstract nature of algorithms, expressive animations which illustrate these processes have become critically important educational tools. Another important feature of online learning environments is to what extent the user should be involved in the learning process. Previous research in this field has produced mixed results. While some studies emphasize that there is a benefit to user control, others conclude that interrupting the animation process can also have negative effects. Taking into account this previous work we have used a novel online learning tool (AlgoRythmics) which includes visualizations of ten basic computer algorithms (searching and sorting strategies). In this environment three levels of interactivity have been defined: no-interactivity (passive viewing of instructional material: students are independent observers), half-interactivity (students are partially involved: at specific key moments the animation suddenly stops, and user interaction is required) and full-interactivity (full control is given to users: students are invited to orchestrate the algorithm by predicting the entire operation sequence for a given input). We focused on the AlgoRythmics illustration of the Shell sort algorithm and, more specifically, on the influence that the degree of interactivity has on students' learning. We examined 137 first year undergraduate students (14% females) who were divided in three "equivalent" subgroups based on their prior knowledge (0, 1-3 or 4 years of programming during high school studies). We chose the Shell sort algorithm since none of the participants were familiar with this sorting strategy. The three instructional conditions assigned to the three subgroups were: no-, half- and full-interactivity. Our results show that there are no significant differences between students' performance from the three specific subgroups. This finding is in line with some previous research results that emphasize that each interactivity level might have both positive and negative effects. Since students' learning styles are different, an important characteristic of online learning environments should be that they provide the possibility for everyone to choose the most appropriated interactivity level.