Procedure (or method) calls are a basic computation mechanism found in virtually every language. A procedure call may or may not create aliases for parameters. Understanding aliasing is critical for comprehending how programs will behave, with impact on other concepts such as parallelism.

In this paper we study the awareness and descriptions of aliasing behavior in two college-level audiences. The paper measures their understanding of aliasing, analyzes their written explanations of procedure calls, and identifies problems with their knowledge. In particular, we show that even upper-level students suffer from difficulties that instructors might have assumed have long since been addressed.