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Abstract This study examined how literal symbols affect students' understanding of algebraic expressions. Middle school students (N = 322) were randomly assigned to 1 of 3 conditions in which they were asked to interpret an expression (e.g., 4c + 3b) in a story problem. Each literal symbol represented the price of an item. In the c-and-b condition, the symbols used were the 1st letters of the items (e.g., price of a cake in dollars = c; price of a brownie in dollars = b). In the other 2 conditions, c and b were replaced with nonmnemonic English letters (x and y) or Greek letters (? and ?). Incorrect interpretations of the expression were most common among students in the c-and-b condition. Moreover, students in this condition were more likely than students in the other conditions to misinterpret the symbols as labels for objects (e.g., c stands for cake). An analysis of participating students' textbooks revealed that mnemonic symbols were used correctly and were not uncommon. Results suggest that the use of mnemonic symbols may hinder students' interpretation of algebraic expressions.
