Is it a fact? Timed arithmetic performance of children with mathematical learning disabilities (MLD) varies as a function of how MLD is defined.

Poor fact retrieval is a frequently reported characteristic of children with mathematical learning disability (MLD). To better understand the nature and specificity of poor fact retrieval in MLD, in the present study, we examined eighth graders' accuracy on timed addition and multiplication problems of varying levels of difficulty. We compared the performance of 16 children with deficient math achievement (MLD), 19 children with below average (but not deficient) math achievement (LA), and 100 typically achieving (TA) children. Children in all three groups made errors. Errors made by children in the LA group were more numerous, but comparable in type, to those observed for typically developing children. Errors made by children with MLD were more numerous still, and included errors that differ qualitatively from those in the LA and TA groups. Thus the way in which performance linked to "math difficulties" differs from that of typically achieving children varies as a function of how we define math disabilities (MLD vs. LA). Moreover, the frequency and types of errors made by individuals varied within the MLD group, highlighting group heterogeneity even when using strict criteria to define this group of children. Finally, the types of errors made by children with MLD reflect reliance on processes other than retrieval to solve these alleged "math facts."