They're built in, like most cognitive abilities. After all, you never learn how to take a 2 dimensional pattern of light hitting your retina and turn it into a

They're built in, like most cognitive abilities. After all, you never learn how to take a 2 dimensional pattern of light hitting your retina and turn it into a 3 dimensional model of your environment. Ditto for locating the source of sounds. And, while you learn a specific language, none of us have to develop the general skill of learning a language from scratch as toddlers.