BEHAVIORAL DIFFERENCES 295 



are present in 'DBA/2 mice and the strain very quickly returns to its own behavioral 

 equilibrium. In this case the return is maladaptive because glutamic acid helps the 

 organism. The initial doses produce the effect, but an escape occurs with subsequent 

 doses. The difference between the effect of glutamic acid in the two strains is clearly 

 due to a difference in genetic capacity. 



Another important point concerns the definition of a natural unit of behavior 

 or phenotype. Is gross bodily activity, which is the sum of various behaviors, any 

 more a natural unit than fighting under confined conditions? The ethologists have 

 attacked the problem of the natural unit by making the behavior misfire. Imprinting 

 to an inappropriate object identifies an entire behavioral complex and provides one 

 method for extracting a natural biological unit, and this, in a sense, is a kind of 

 natural phenotype. 



Another way of defining a natural unit is to grasp whatever genetic difference 

 exists, whether it be a strain difference or a genie difference, whether it involves climbing 

 up on a pole, turning an activity wheel, agressiveness under confinement, or whatever, 

 and consider that this is that part of the iceberg that is above water and that only by 

 analyzing what genetic complex is behind it and then working back to the causal 

 mechanism as well as forward again to produce the phenocopy, can the part of the ice- 

 berg that is below water be found. A behavioral phenotype is the result of research 

 and not something that is given at the beginning. 



This, to me, is behavioral genetics. It involves a physiologic-genetic approach to 

 behavioral phenotypes. It is in no way a new science. If one reads the earlier genetic 

 literature, one finds that when Mendelian traits were described, many of them were, 

 broadly speaking, behavioral. They ranged all the way from mutations that affected 

 the sense organs, such as rodless retina, 692 to position preference in coach dogs. 695 

 That behavior is under some genetic control has been known for a long time, and this 

 so-called phenotypic approach has not advanced our knowledge of it very far. The 

 physiologic-genetic approach is needed to bring about such an advance. Darwin 

 had a prototype of a strain difference in behavior that he refers to in The Expression 

 of the Emotions of Man and Animals. He describes a little hybrid girl who was half 

 French and half English. When she was still very young, she shrugged her shoulders 

 in a completely un-English way, although reared in an English environment. On the 

 phenotypic side, we have not progressed much beyond this in so-called behavioral 

 genetics to date. We shall not progress unless a physiologic-genetic approach is 

 followed as outlined in these comments. 



Dr. Fuller: The two previous speakers have been discussing two different 

 viewpoints. Dr. Scott emphasized the phenotypic orientation towards behavioral 

 genetics, in which one starts with behavioral patterns which are defined as a phenotype 

 and works backward to find out how they are inherited. The advantage of this approach 

 is that it deals with behavior important to the organism and significant in evolution. 

 However, one may have to sacrifice genetic clarity for the sake of behavioral significance. 

 In the genotypic approach one uses genes as a form of treatment. The effects of the 



