Starch: Inheritance of Mental Traits 



93 



and quantity of soil did not alter the 

 relation of vigor between inbred and 

 hybrid plants. The marked increased 

 rate of growth and development of 

 the hybrid plants is shown in Figures 

 32 and 33 which represent the same 

 plants, a time interval of six weeks 

 between photographs. In Figure 34 the 

 hybrid plant is in flower and has been 

 bagged in order to secure the hybrid 

 seed. The inbred plants are so much 

 slower that they have not started to 

 produce a flowering stalk. The simi- 

 larity of behavior of maize and Crepis 

 regarding inbreeding and crossing of 



inbred strains indicate a certain simi- 

 larity of germinal conditions between 

 a species long domesticated and thus 

 subject to artificial selection and a 

 wild species which has never been sub- 

 jected to such selection. 



This brings up a question whether 

 domestication of a cross-pollinated 

 species accompanied as it is with arti- 

 ficial selection changes in any appre- 

 ciable extent the relations of the factors 

 conditioning vigor, rate of growth and 

 development from the relations they 

 had in the wild species from which the 

 domesticated species originated. 



INHERITANCE OF MENTAL TRAITS 



Evidence that Heredity Determines the Make-up of the Mind as Well as the 



Body Is Reviewed by Starch 



Paul Popenoe 



SO LONG as psychologists de- 

 pended on introspection for their 

 science, it was possible for some 

 of them to believe that mental traits 

 are not inherited. The doctrine of 

 the child's mind as a blank sheet of 

 paper, on which the environment and 

 the teacher wrote their autographs, had 

 followers. 



But with the development of precise 

 and objective methods in psychology, 

 students were rapidly forced to realize 

 that the mind was not in a realm by 

 itself; for they came up against facts 

 that could be satisfactorily interpreted 

 only by the supposition that differences 

 in mental ability are inherited in the 

 same manner as, more obviously, are 

 differences in physical ability. 



Thus it is, according to Daniel 

 Starch, that among psychologists "the 

 view held by most scientific students of 

 the problem today gives weight to both 

 elements, with perhaps the major em- 

 phasis on heredity." 



Dr. Starch's recent and well-docu- 

 mented book^ on educational psychol- 

 ogy discusses three of the numerous 

 lines of evidence that have caused this 

 recognition of the importance of hered- 



ity. These lines are: (1) The similarity 

 of abilities among related persons; 



(2) the influence of uniform environ- 

 ment on different original abilities; and 



(3) the influence of different environ- 

 ments upon similar original abilities. 



THE HISTORICAL APPROACH 



L Correlation of abilities may be 

 studied most conveniently either at one 

 extreme of the population or the other; 

 either among those who are talented or 

 among the feeble-minded and other de- 

 fectives. The problem was first at- 

 tacked, historically speaking, among 

 the eminent, by Francis Galton, and 

 was followed up much later by Freder- 

 ick Adams Woods. 



Galton made a study [published in 

 1869] of 977 eminent men, each of 

 whom was the most eminent among 

 4,000 persons. He proceeded to de- 

 termine how many relatives of equal 

 eminence and of varying degrees of re- 

 lationship each person possessed. In 

 this manner he found that these 977 

 men had the following relatives of a 

 like degree of eminence: Fathers 89, 

 Brothers 114, Sons 129, Grandfathers 52, 

 Grandsons 53, Uncles 53, Nephews 61; Total 

 535. 



1 Educational Psychology, by Daniel Starch, Ph.D., University of Wisconsin. 

 The Macmillan Co., 1920. Pp. 473, with 96 text figures. 



New York: 



