In one test Charles was shown a pair of digits and asked to name the larger number. The bigger the gap, the faster most people can do this: they say “nine” fast

In one test Charles was shown a pair of digits and asked to name the larger number. The bigger the gap, the faster most people can do this: they say “nine” faster when shown 9 and 2 than when shown 9 and 7. But with Charles, the reverse was the case—and the researchers could see why. Rather than telling the answer directly, he was counting on from one number (on his fingers) until he got to the other, which meant he must have started at the smaller, or he got to ten, in which case he must have started at the bigger. Most strikingly, he lacked the fundamental numerical ability possessed by most newborns: being able to tell the number of objects in a small group simply by looking. When asked how many dots were on a sheet of paper, he counted on his fingers—even when there were only two. Charles’s deficit, though severe, seemed to affect his numerical abilities alone. Numerical deficits in people of otherwise normal abilities can be even more striking in cases of brain damage. Lisa Cipolotti, a neuropsychologist, studied a Signora Gaddi, who used to run a hotel and keep its accounts. After a stroke she could find the number of things in a small group only by counting—when asked how many arms a crucifix had, she got Dr Cipolotti to hold out her arms so she could count them. Signora Gaddi’s problems seemed to affect only numbers. She could still read, speak and reason, remember historical and geographical facts, and order objects by their physical size. In fact, Signora Gaddi’s difficulties went even deeper than Charles’s. The stroke which damaged her innate understanding of small numbers also robbed her of the entire numerical edifice built on that foundation. For her, numbers stopped at four. When asked to count up from one, she got to four and no further. If there were more than four dots on a page she could not count them. She could not say how old she was or how many days were in a week, or even tell the time. Scary.