Recursion in Secondary Computer Science Education: A Comparative Study of Visual Programming Approaches

While recursion is a fundamental technique in computer programming, it is challenging for novices, for example since it requires tracing non-linear and hierarchical sequences of execution. Though algorithm visualizations and visual programming may be helpful, such tools need to offer sufficiently expressive environments that support active, constructivist learning via exploration and experimentation. In this study, we investigated whether Algot, a visual programming language that relies on a novel programming-by-demonstration paradigm, is effective for teaching recursion to 1417 year old students, and whether it compares favorably to the popular visual programming language Scratch. We conducted an experimental study with 23 participants where they learned recursion in a video tutorial using Algot and Scratch, worked out code exercises in each respective language, and then solved a post-test on recursion. Despite the participants being more familiar with Scratch than Algot, our results indicated that students instructed with Algot demonstrated a significantly better understanding of recursion (Bayes Factor = 14.09, p = 0.005, Cohen's d = 1.30). We also found that students reported a similar level of enjoyment of each language. These findings provide preliminary evidence about the effectiveness of the programming-by-demonstration paradigm, as implemented in Algot, in aiding the comprehension of complex programming concepts like recursion.