Rexroad, C. N. (1940). The mechanism of heredity and some implications. In C. N. Rexroad, Psychology and personality development (pp. 270-297). New Braunfels, TX, US: Christopher Publishing House.
http://dx.doi.org/10.1037/14780-011
No person questions the fact that inheritance accounts in part for what he is—in build, in strength, in resistance to disease, in emotional stability, in intellectual strength, in ways of thinking, in feeling and acting; but when it comes to the question of the exact extent to which heredity determines a particular anatomical or behavior trait, there are the widest differences of opinion. These differences exist partly because of ignorance regarding the transmission of inheritance, partly because of accepting as evidence data which do not constitute true evidence, partly because of difference in definition, but largely because of insufficient data on which to base an answer. The problem of determining the influence of heredity in man is extremely difficult for many reasons, but progress is being made. The purpose of this chapter and the next is to summarize what is now known, as well as to determine as best we can what sort of data are required for valid evidence. Basic to this task is an understanding of the way an individual obtains his inheritance. (PsycINFO Database Record (c) 2016 APA, all rights reserved)