The name of a famous eugenics study in 1912. Martin Kallikak was a well-known Quaker. He had relations with a 'dullard', siring children, then settled down with 'an industrious Quaker maid'. The legitimate children were judged to be successful, the illegitimate children less so. Since the kids grew up two miles apart, researchers concluded that the environment was the same, and therefore the only variable was the genes of the mother.

The 'successful' Kallikaks, some of which where judges and professors, had few children. The illegitimate Kallikaks often had many children. This gave creedence to the theories that idiots replicate faster than smart people.

The studies were published with photographs. The 'unsuccessful' side of the family were shown as unattractive and sinister-looking, and the 'successful' side of the family was shown to be more attractive. This alone swayed many opinions.