As the third in a series of projects investigating commonsense computing -- the relevant knowledge that students have before any formal study of computing -- we examine students' commonsense understanding of concurrency. Specifically, we replicated (with modifications) an experiment by Ben-David Kolikant. [2] Ben-David Kolikant's data were gathered from high-school seniors who had previously studied computing, at the beginning of an advanced class in concurrent and distributed programming. Modifying one of her questions to reflect our students' lack of background, we asked students at five different institutions, in the first week of CS1, to describe in English the problems that might arise when more than one person is selling seats to a concert.

Almost all students (97%) identified the problem of interest -- that a race condition may occur between sellers. 73% of students identified at least one possible solution. We found that the categorizations developed by Ben-David Kolikant were also meaningful when applied to our data, that our beginning CS1 students are more likely to give centralized solutions (as opposed to decentralized ones) than Ben-David Kolikant's concurrency students, and that the granularity of solutions is finer among the more experienced students.