The latest edition of The Economist has an interesting article about whether our ability to count and estimate quantity is an innate ability that we have from birth.
The article covers studies on babies, people who speak languages that only have number words for “one”, “two”, “few” and “many”, people who have never developed certain maths skills and others who have lost specific number abilities after brain injury:
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‚Äîwhen asked how many arms a crucifix had, she got Dr Cipolotti to hold out her arms so she could count them. Signora Gaddi‚Äôs 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‚Äôs difficulties went even deeper than Charles‚Äôs. 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.
Link to Economist article ‘Easy as 1, 2, 3′.