Assessing Children's Logo Debugging Skills with a Formal Model

Abstract

In this article, we propose a new way to assess children's acquisition of debugging skills in a LOGO environment. The assessment procedure is based on an explicit and precise model (in the form of a computer simulation) of good debugging skills. The model has four stages: 1) evaluating the program's planned and actual outcomes to determine that debugging is necessary, 2) identifying the bug by using descriptions of the discrepancy between the planned and actual outcomes to propose potential bugs, 3) locating the bug by using clues about the structure of the program to narrow the search, and 4) correcting the bug and retesting the program. We describe model-based measurements of the LOGO debugging skills actually acquired by students in a “typical” LOGO graphics course. Nine seven- to nine-year-olds were given twenty-four hours of LOGO training over a three-week period. Students learned the editing and command generation skills prerequisite to debugging but were not able to interpret commands and use clues to identify, locate, and correct bugs. We conclude by discussing objectives for teaching the model's debugging skills directly.