J. P. Scott, Ph.D., and John L. Fuller, Ph.D. 



BEHAVIORAL DIFFERENCES 



Rather than repeat material already familiar to geneticists, we shall discuss in 

 this paper special methods and problems peculiar to behavioral genetics. These special 

 problems arise from the fact that any study relating genotype to behavior requires 

 some extension of the concept of phenotype. Ordinarily the phenotype of an organism 

 is expressed in terms of its structure or color, and these characteristics are relatively 

 similar under a variety of conditions. A behavioral phenotype, however, is transient 

 and can be evoked only under a specified set of conditions. The choice of these condi- 

 tions and the nature of the phenotypic measurement are the major concern of this 

 paper. 



Behavior, while it has a physiologic basis, is usually defined as the activity of an 

 entire organism rather than in terms of the activity of a single organ system. Thus 

 behavior is one additional step removed from primary genie action, and the genetics 

 of behavior occupies a position somewhere between physiologic and population 

 genetics. 



Because of the relative remoteness of the behavioral phenotype from the gene, 

 emphasis 410 has been placed on the noncongruence between genetic organization and 

 behavioral organization. Noncongruence might at first thought imply that genetics 

 has very little to do with behavior, but the empiric evidence is quite the contrary. 

 Almost any measure of behavior can be shown to be affected by genotype, and, con- 

 versely, almost any major genotypic difference can be shown to affect behavior. Thus 

 the genetic analysis of behavorial variation is, and will continue to be, a lively field of 

 investigation. 



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