Date of Award


Document Type




First Reader

Dr. Weldon E. Vogt


The general issue of the significance of genetic contributions to individual differences may be approached in two ways, through population genetics and through physiological genetics. The first has no logical meaning when applied to an individual, for his whole genotype and total life experience contribute to every aspect of his behavior, and their influences cannot be separated. The second is rather light on the emphasis of environment and its influence.

The two approaches to the problem on individual differences complement each other. Knowledge of heritability is paramount when one attempts to change phenotypes by selection. Possibly the most significant contribution of behavior genetics is its documentation of the fact that two individuals of superficially similar phenotypes may be quite different genotypically and respond in completely different fashion when treated alike. Knowledge of how genes produce effects on behavior is often sought for its practical importance. If one can counteract the effect of a genetic lesion by biochemical means, seriously defective individuals may be restored to health. The dual approach to the problem of individual differences has dictated a division of this paper into two sections followed by a general summary.



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