Last time we discussed "acalculia,"the condition whereby people with neurological damage brought on, for example, by stroke, find themselves suddenly unable to work with numbers.
This can be the case even while they may remain otherwise largely unimpaired. The number-specific nature of this disorder raises all sorts of intriguing questions about how numbers are represented in the brain. In fact, some scientists now argue that the ability to understand and work with numbers is something that evolution has "hard-wired" into our brains. In other words, you are born with a number sense, at least in a basic way.
Evidence for this point of view comes from the research done by child psychologist Karen Wynn at the University of Arizona. Since you can't ask an infant whether she understands numbers or not, Wynn used an indirect method. She showed infants one Mickey Mouse going behind a screen, followed by a second Mickey; but when the screen was dropped, only one Mickey was there. In such mathematically-incorrect scenarios, Wynn found that infants stared a half second longer than if two Mickeys were present when the screen dropped. This suggests that they expected two Mickeys to be there. And that means 1+1=2, even for a toddler.
In other tests, Wynn has found that infants are also able to count events, such as the number of times Mickey jumps. An event is a different kind of thing than an object, although both can be counted. The ability of infants to do so strongly suggests that there is a natural sense of one, two, three written into our brains from a very early age.