This paper was presented at the American Psychological Association Convention in September 1959; and in a modified version at the Annual Meeting of the American Society for Human Genetics in August 1959. A new method of dichotomic analysis, essentially a continuous series of goodness-of-fit tests was applied to test data from twins. Prediction was fairly well substantiated leading to the conclusion that there was good evidence for a basic dichotomy of genetic origin for specific traits even though the actual models for inheritance could not be ascertained.
