Counted out

日期：2017-09-15 02:38:22 作者：舜彬 阅读：

By Duncan Graham-Rowe A NEW test could reveal how many children are afflicted by a poorly understood condition that is the numerical equivalent of dyslexia. Dyscalculia is thought to be a disorder of the brain’s left parietal lobe, situated above the ear, that affects numerosity, an innate sense of “manyness”. Dyscalculics struggle to relate quantities in the real world to numbers. They would have difficulty reading their score after throwing dice, for example. Existing tests for dyscalculia measure whether people are significantly bad at arithmetic given their age, educational background and IQ. But Brian Butterworth, a cognitive neuropsychologist at University College London, believes this approach is flawed. “A standard test would not distinguish between someone with dyscalculia and someone who hated their maths teacher,” he says. In Butterworth’s new test, subjects are asked to perform two tasks. The first is to say how many dots there are in a visual display. Most people could instantly put a number to a group of, for example, three dots, but dyscalculics seem to resort to laborious methods such as counting, a function performed by a different part of the brain. The other task is to tell which of two numbers is larger. Again, dyscalculics find this very hard. Because dyscalculics take much longer to complete the tasks, Butterworth thinks his test will be a reliable way of diagnosing the condition. His team is now imaging the brains of people it has identified as dyscalculic to put this idea to the test. “If it allows us to tell that a child’s mathematical inability isn’t due to behavioural factors, that it is biological, then one can set out to help the child,