Algebra is often considered as difficult and mysterious doctrine due to numerous symbols that represent mathematical notions. Results of the research on students' interpretation of literal expressions show that only a small number of students are ready to accept that a letter can represent a variable. The aim of this research with students of the fourth grade of elementary school was to examine the impact of the use of various symbols, which represent the relationships between the quantities, on students' understanding of the meanings of literal expressions. We used experimental method (with one group) and the testing techniques (pre-test and final-test comparisons). The research results show that the iconic representation of the structure of literal expressions, namely, giving meaning to a term through its reliance on certain schemes in the learning process, significantly affects the ability of students in modelling generic quantitative relationships, and in the development of the meaning of letters in the role of algebraic variable.