Ordinal processing in children with mathematics learning disabilities

The present study examined whether a numerical order processing deficiency is a key factor underlying mathematics learning disabilities (MLD) in children, or whether children with MLD have a general ordinal processing deficiency. Twenty-one children with MLD were tested and compared to 32 children without MLD on three ordinal tasks (numbers, letters, lines), and two number magnitude tasks. The results demonstrate that children with MLD have a general ordinal processing deficiency as they displayed difficulties with ordered and non-ordered sequences of all three types of information. Moreover, the severity of these difficulties was equivalent for all three types of information. On the number and letter ordinal tasks they displayed reversed and standard distance effects effect akin to the controls, but larger standard distance effects on the line order task. Moreover, the children with MLD displayed difficulties with symbolic number magnitude comparison but displayed a typical standard distance effect. The combined findings of the study suggest that children with MLD have an impaired ability to access magnitude information from numerical symbols, in addition to their general ordinal processing deficiency.

Educational relevance statement

This study shows that children with mathematics learning disabilities (MLD) have severe general problems with ordinal processing (i.e., “which position or rank an item has in a set or sequence of items”), for example, judging whether three numerals are in correct order (1–2–3) or not (2–3–1). These findings suggest that screening procedures to detect children with MLD or those in risk of developing mathematical difficulties should not only include measures of number magnitude processing (i.e., “how many”), and arithmetic, but also symbolic and non-symbolic number ordinal processing as well as non-numerical ordinal processing (e.g., letters). Similarly, school support aiming at preventing mathematical difficulties in young children should target both number magnitude and number ordinal processing.