572 HUMAN BIOLOGY 



DOES GOOD ENVIRONMENT OR TRAINING IMPROVE HEREDITY? 



It has long been an article of faith with extreme environ- 

 mentahsts that improvement of environment will improve 

 not only development, but also heredity itself. Doubtless 

 inheritance factors can be modified in rare instances by 

 changes in environment. It has been shown that such 

 modifications can be produced by x-rays, though these are 

 almost always of a degenerative sort. But there is no satis- 

 factory evidence that good environment will produce 

 improvements in heredity or bad environment, bad heredity: 

 no evidence of the inherited effects of use or disuse or 

 training. A given kind of wood, such as pine, oak or mahog- 

 any, may be shaped into chairs, tables or doors by the tools 

 and forces that act upon it, but the wood itself does not 

 change its nature. Similarly a given kind of egg, such as 

 that of a fish or frog or bird may have its development 

 shaped and modified to a certain extent by the environ- 

 ment that acts upon it, without changing its fundamental 

 nature or heredity. 



In the mental and social fields, as well as in the physical, 

 there is no satisfactory evidence that the effects of use or 

 disuse are inherited in the biological sense. Numerous claims 

 of such modification of heredity have been made. One of the 

 most important of these was announced in 1923 by the 

 distinguished Russian physiologist Pavlov who found that 

 it took about 300 trials to teach the first generation of white 

 mice with which he experimented to come to food on the 

 ringing of a bell, the second generation came in about 100 

 trials, the third in 30, the fourth in 10, and the fifth genera- 

 tion in 5 trials. Here was apparently an amazingly rapid 

 inheritance of the effects of training, indeed it was so at 

 variance with all other experience in animal training and in 

 human education that it was generally discredited in spite of 

 the scientific standing of the author. Recently Pavlov has 

 admitted that his results were based on errors and he with- 

 draws his claims as to the inheritance of the effects of train- 

 ing (McDougall, i927).ThepsychologistWm.McDougall,has 

 recently (1927) published the results of a very careful and 

 extensive study of the inherited effects of the training of 



