Human beings do not mate at random, but according to religious, cultural, and personal preferences. This type of assortative mating has led to differences in human populations. Eugenicists realized that assortative mating did not always produce the best offspring, so sought ways to popularize what they considered to be good marriages. Francis Galton urged the brightest and the healthiest individuals to marry each other. He found an ideal situation in German university professors (then all male) who tended to marry the daughters of professors or their female graduate students. This positive expression of eugenics encouraged the selection of good mates through popular health books and Fitter Families Contests held at state fairs. The training of field workers at the Eugenics Record Office included exercises to help them analyze mate preferences and make better eugenic choices.
The negative side of eugenics sought to prevent so-called "defectives" from selecting mates of their own kind and, thus, perpetuating degenerate inheritance. Consanguinous marriages between relatives were thought to be the source of "degeneracy" in many "backwoods" families. The mentally handicapped, and even epileptics, were prohibited from marrying and liable to be sterilized in more than 25 states. Alexander Graham Bell feared that coeducational schools for the deaf might lead to formation of a "deaf race" of humanity. Harvard scientist Lucien Howe lobbied for laws requiring that blind persons post a bond to cover the costs of caring for any blind children.
Eugenicists were often called upon to comment on family pedigrees, diagnose genetic disorders, and offer advice about the fitness of proposed marriages. This sort of "eugenic counseling" was a forerunner of modern genetic counseling, which was given its name in 1940 by Sheldon Reed at the University of Minnesota. He conceived of a service that would provide families factual information about their hereditary disorders and how they are transmitted from parents to children. Reed took care to separate genetic counseling from eugenics, which was highly directive — that people should be "prescribed" a correct course of action. To the contrary, Reed thought genetic counseling should be non-directive — that people should be provided with the information needed to make their own decisions. Clients needed to make judgments on how to use that knowledge.