Alas for Volapük

that his/­her monozygotic twin and a 39% chance that a dizygotic twin will also be dyscalculic. The link also exists between dyscalculics' parents and siblings: around half of the all first-degree family members of a dyscalculic also have dyscalculia (mothers, 67%; fathers, 41%; brothers, 53%; sisters, 52%), and 43% of the second-degree relatives. This prevalence is around tenfold higher than expected for the general population. However, there are no gender differences. Is there any comorbidity with other developmental problems? People that have developmental problems, such as dyslexia, attention deficit hyperactivity disorder (ADHD), neurological problems, such as epilepsy, or genetic disorders of the X chromosome, are at greater risk than the normal population of being dyscalculic. In these cases, however, the dyscalculia might be a secondary problem, and might not stem from a core deficit for numerical processing per se. For example, a child with ADHD might not be able to solve arithmetic problems successfully due to failures in planning and organisation. Aside from comorbidity with other developmental problems, it has also been suggested recently that people suffering from dyscalculia might have impaired abilities in processing other non-numerical magnitudes such as physical size. What is the consequence of dyscalculia for one's life? The consequences of poor numeracy in today's world are significant and long-lasting: initial problems in school subjects that require maths later translate into reduced employment opportunities. Not surprisingly then, poor numerical abilities correlate with an adult's economic and social status and psychological well-being (it is no coincidence that all the happy, wealthy readers of Current Biology are above normal in their numerical abilities). Surprisingly, for women, deficiencies in numerical abilities can count even more than other disorders, such as poor literacy. Can it be alleviated? In contrast to dyslexia, where the neurobiological basis has been convincingly demonstrated and some effective treatment possibilities have been introduced, remediation for dyscalculia is in its infancy. There are some current attempts to design training programs, including adaptive computer games for children, which will hopefully enable us in the long run to remediate dyscalculic behaviour. However, remediation programs still need to be validated in large group trials including a control group in order to examine placebo-like effects. The future success of remediation programs rests on accurate and early diagnosis of subtypes of dyscalculia, and referring the person to the appropriate intervention program. Hopefully, better knowledge of both normal and abnormal numerical processing at the …