Dyskalkulie und legasthenie: Same or different?

Dyscalculia and dyslexia are reported to frequently occur in combination. It is often assumed that the two disorders are caused by the same underlying deficits, however, empirical findings do not seem to support deficits in semantic memory or working memory as a common cause of dyscalculia and dyslexia. Recent research suggests that dyscalculia and dyslexia are independent from each other on the neuro-cognitive level and are based on different deficits. More specifically, a deficit in basic processing of numbers and numerosities is assumed to underlie dyscalculia while dyslexia is generally accepted to be caused by deficits in phonological processing. It is well known that dyscalculia frequently co-occurs with a range of other disabilities (attention deficits, non-verbal memory deficits, language deficits, etc.), however, it is currently unclear if these disabilities play any causal role in developmental maths disability.