Abstract:

Mental computations constitute an important part of functional mathematical knowledge and skills. Important prerequisites for effective mental computations are knowledge of number facts and possession of strategic competence. Among students facing considerable problems with mental computations, students with learning disabilities (LD) have a prominent place both because of their high number in school population and because of the characteristic mistakes they commit. The present research investigates differences between students with and without LD in mental additions and subtractions with results up to 100. The participants were 60 primary students of the 5th and 6th grades (30 with and 30 without LD), who were asked to provide oral answers to 16 problems of the following categories: 2-digit additions with and without transfer, and 2- digit subtractions with and without borrowing. Results analysis was based on the model of strategic change by Lemaire and Siegler (1995). It was found that students with- differ significantly from students without LD both in the repertoire of the strategies they use for mentally calculating the results, and also in the frequency with which they use various strategies. Moreover, students with LD were found as less accurate than their typical peers in computing results in all of the above- mentioned categories of addition and subtraction, apart from the category of 2-digit additions without transfer. Group differences with regard to the time elapsed between problem presentation and student reaction were not significant. In reference to the nature of the errors conducted by the two groups in additions, it was found that students with LD presented mainly number fact errors, place value errors, and fewer errors regarding transfer or combinations of errors. In contrast, students without LD presented low numbers of errors of all kinds. In subtraction, students with LD exhibited mainly place value errors and error combinations, and to a lesser extent number fact errors, and errors with borrowing. Similar errors were presented by students without LD, although to a lesser degree. Results are discussed in terms of their implications for daily school practice and the features of the programs through which students with considerable difficulties in mental computation could be supported.

Keywords:

Mental computations, Learning Disabilities, computation strategies.