Key: Better American Families III 



109 



reversal of the process and the produc- 

 tion of an increasing proportion of 

 children with low ability. We would 

 appear to have here then, segregation, a 

 real alternative inheritance, with pos- 

 sibly units of progressively higher po- 

 tency as we pass from strains having a 

 low level of this ability to those with 

 superior endowinent. 



AGGRESSIVENESS 



This trait-complex may be defined as 

 energy and courage in the undertaking 

 of new projects. It will be seen at once 

 that the grades of this character cannot 

 be fixed with the definiteness possible 

 when dealing with number. They were 

 evaluated with reference to the eco- 

 nomic and social opportunity, physical 

 and mental limitations and the effect of 

 example on suggestible individuals. The 

 distribution of 282 individuals, the 

 product of eighty matings was as 

 follows : 



with which one follows a line of activity 

 is due mainly to his capacity for forming 

 habits in conjunction with his dominat- 

 ing interests. While the latter have no 

 doubt heritable elements in what are 

 usually known as "aptitudes," still they 

 are aflected by all sorts of extraneous 

 influences. Such native qualities as 

 pride, endurance, independence, ob- 

 stinacy also have their role in its mani- 

 festation. When, however, it is remem- 

 bered that small children show a wide 

 range in this characteristic while im- 

 beciles, who are incapable of conceiving 

 a chain of related purposes, likewise 

 show a wide range, this trait-complex 

 may well be regarded as having heritable 

 elements whose behavior may be profit- 

 ably investigated. 



The children from eighty matings to 

 the number of 269 were classified into 

 three groups, and the results compared 

 with the theoretical expectation accord- 

 ing to Mendel's Law. 



Here again the realized percentages 

 would indicate the heritability of this 

 trait-complex in accordance with the 

 theory of segregation of determiners for 

 the trait-complex. The slightly wider 

 discrepancy between the expected and 

 the realized results is no doubt due to 

 the difficulty of evaluating the character. 

 It will be observed that the discrepancy 

 is considerable only where both parents 

 are moderately aggressive, or where one 

 has a very low grade while the other has 

 a high grade of the trait. In both cases, 

 the offspring show greater resemblance 

 to the parents than the hypothesis 

 would lead us to expect. 



PERSEVERANCE 



In dealing with this trait-complex, we 

 are again confronted by the difficulties 

 involved in its evaluation. As in the 

 case of aggressiveness, the social inheri- 

 tance plays a far greater role in its 

 manifestation than it does in the ability 

 to handle numbers. The persistence 



Here again, there is some discrepancy 

 between the actual and the theoretical 

 results which may well be laid to diffi- 

 culties in grading and the effect of 

 exogenous elements on the manifesta- 

 tion of innate tendency. Making due 

 allowance for these factors, the conclu- 

 sion seems warranted that there are 

 heritable elements in perseverance whose 

 behavior is in accord with the principle 

 of segregation. 



CONSTRUCTIVE ASPECT OF SEGREGATION 



Our histories furnish many interesting 

 examples where there appears to have 

 been an effective building up of trait 

 combinations through fortunate matings 

 in successive generations. Thus in line 

 A, aggressiveness, perseverance, cal- 

 culating ability and finally mechanical 

 ability all converge from strains posses- 

 sing these abilities to produce in the 

 sixth generation unusual mechanical and 

 mathematical aptitude, which with the 



