Arabic digit processing in adults with mathematical learning disability

The processing of Arabic digits is a core difficulty of children suffering from mathematical learning disability (MLD). Dominant accounts assume a semantic impairment affecting either the magnitude representation per se or its access from numerical symbols. But recent data have raised the hypothesis that the impaired processing of Arabic digits may be explained by a selective deficit of digit visual recognition (i.e., recognising a symbol as one of the digits, no matter its identity or numerical meaning). This study aims at testing whether the difficulty to process Arabic digits remains prevalent in adults with MLD and whether it is effectively associated with a digit visual recognition deficit. To do so, we compared 19 adults with MLD to 19 matched controls in an Arabic digit comparison task that required to identify the largest of two digits, and in an Arabic digit lexical decision task that required to decide whether a visual stimulus is a digit or not. The results showed that MLD participants took more time than control participants to perform the comparison task. In contrast, their performance in the digit lexical decision task was within the range of the control participants. Overall, this finding indicates that adults with MLD continue to experience difficulties to process the magnitude of Arabic digits efficiently, and this cannot be explained by a visual recognition deficit for Arabic digits. We conclude that their difficulties are best explained by an impaired representation of number magnitude or by an impaired access to this representation.