'Number Sense'

SquareCircleZ blog has a nice post up on "Number Sense," the subject and title of a 1999 book by psychologist Stanislas Dehaene that I too would recommend about the innate "sense" of numbers/mathematics we (and even some animals to a limited extent) seem to be born with (also, Keith Devlin covers some of the same subject matter in his 2000 volume "The Math Gene"):

http://www.squarecirclez.com/blog/number-sense/4957

...interesting reading for the scientist/mathematician and non-scientist alike.