Non-determinism in CS high-school curricula

One of the units in the relatively new high school CS curriculum which is being implemented in Israel is a theoretical unit on computational models. It includes deterministic and non-deterministic finite automata, regular and non-regular languages, closure properties of regular languages, pushdown automata, closure properties of context free languages, Turing machines, the Church-Turing thesis and the halting problem. This paper focuses on part of a study we conducted on the unit, dealing with the topic of non-determinism of finite automata. One of the aspects dealt with was how students perceived non-determinism. 339 students were given a relatively complicated regular language, and asked to construct a finite automaton that accepts this language. We found that many students did not choose the easiest way to solve the problem: Many students preferred to construct a deterministic automaton, even though constructing a non-deterministic automaton for the language is much simpler. We analyze and categorize the students' solutions, thus shedding some light on their perception of the abstract concept of non-determinism.