VanLehn, K. (1983). On the representation of procedures in repair theory. In H.P. Ginsberg (Ed.), the development of mathematical thinking. new York: Academic.

Over the months or years that it takes students to master a procedure such as ordinary place-value subtraction, their performance is characterized by many systematic errors or bugs that indicate a flaw or incomplete understanding of the procedure. Not only are there a very large variety of bugs across the population, but the bugs a student exhibits often shift radically over short periods of time. Nonetheless, there are developmental trends indicating how formal instruction influences the student's (mis-)conceptions of the skill. Repair Theory (Brown & VanLehn, 1980) aims to account for all these phenomena-the large variety of bugs, their short -term instability, and their long-term relationship to instruction.

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