A COMPARATIVE VIEW OF AGGRESSIVE BEHAVIOR
LINCOLN D. CLARK M.D.1
1 Assoc. Professor of Psychiatry, College of Medicine, University of Utah, Salt Lake City, Utah.
A series of studies which illustrate the value of Onychomys leucogaster as a laboratory animal for study of aggression have been reviewed. The aggressive behavior of this animal follows a highly predictable pattern and can be readily quantified. Experimental conditions can be devised whereby it is possible to study factors which influence the first expression of this genetically determined behavioral trait as well as factors which reenforce or inhibit it once it has become established as a response.
Chlorpromazine was found to have an interesting effect upon the aggressive behavior of Onychomys. Medication with this drug in dosage ranges which did not impair fighting ability because of motor toxicity markedly increased the reenforcing value of a fighting experience. A possible interpretation is that the affective state of an animal at the time of a behavioral response, in this instance an aggressive one, alters the effectiveness of the behavior in terms of reenforcement. Chlorpromazine presumably reduces the level of "anxiety" or fear associated with aggression.
Onychomys may also be conveniently employed to study aggressive behavior in social groups. Methods have been described whereby novice, non-fighting colonies of mice may be selectively converted into groups which coexist peacefully with other species, which cooperatively direct aggression toward aliens or which become socially disorganized and suffer from internecine conflict which results in the death of colony members as well as an impaired effectiveness in destroying alien animals.
