Full Idea
Give me a dozen healthy infants, and my own specified world to bring them up in, and I'll guarantee to take any one at random and train him to become any type of specialist I might select - doctor, artist, beggar, thief - regardless of his ancestry.
Gist of Idea
I could take a healthy infant and train it up to be any type of specialist I choose
Source
J.B. Watson (Behaviorism [1924], Ch.2), quoted by Steven Pinker - The Blank Slate
Book Reference
Pinker,Steven: 'The Blank Slate' [Penguin 2003], p.19
A Reaction
This was a famous pronouncement rejecting the concept of human nature as in any way fixed - a total assertion of nurture over nature. Modern research seems to be suggesting that Watson is (alas?) wrong.