Incoming CS1 Students' Misconceptions on Arrays

This paper investigates CS1 students' misconceptions of Java arrays. Each student entering a CS1 course has an initial mental model with a system of beliefs or intuitions about the course domain. The student's initial mental model largely impacts how they integrate new information into it. Oftentimes, these initial mental models are filled with misconceptions. If these misconceptions could be identified early in the semester, educators can attempt to address them with instruction or other educational interventions. But identifying these misconceptions cannot rely on qualitative methods due to the large sections in computing. Instead, we use a quantitative approach to collect assertions that exist in a student mental model. Then we use this representation of mental models to identify misconceptions. We provide a definition of a programming misconception based on mental model theories and use a questionnaire to identify misconceptions based on mental model consistency. We define a mental model as a collection of assertions, and we define a consistently chosen wrong assertion as a misconception. We have broken down Java arrays into a set of parts and state changes. The parts include array name, index, type, and element access. The state changes include array declaration, array instantiation, assignment of literals, and the more general assignment of arrays. We placed 30 wrong assertions multiple times as distractors in our questionnaire. In this paper, we report on our data collection and discuss the 16 misconceptions of arrays found to be held by novice programmers before classroom instruction on arrays. Nine misconceptions were documented for parts components and seven for state changes. Our results show that over half of our participants (out of 93) held at least one misconception before learning arrays in classrooms. CS1 students mostly held misconceptions related to the arrays' declarations (state change), and name, and element access (parts). From our data, the top most common misconceptions were about array declarations and initialization.