man. There is a great effort being made to 
increase the amount of foodstuffs available to man. 
A derivative, if not its motivation, of this effort is 
the widely held opinion that we should produce 
more foodstuffs in order that more people can be 
born and survive. This demands that we maintain 
so long as possible an expanding population. 
There is no doubt that agriculturists and bio- 
chemists have made, and may continue to make, 
marked strides in accomplishing this objective. 
The question remains: What will be the impact 
on the lives of individuals and the structure of 
groups as we progress toward this goal of maximum 
amount of human protoplasm? It is apparent 
that an effort to maximize this goal will simul- 
taneously restrict realization of other needs and 
goals. 
Experimentation on infrahuman sociology and 
population dynamics will assist us in arriving at 
conditions which foster a compromise in various 
goals possible of achievement. The sort of com- 
promise I think we should look for is one which 
imposes some limatations to population expansion, 
yet allows members and complexity of groups 
sufficient to insure benefits derived from coopera- 
tive action, while permitting the individual some 
freedom of action, and freedom of inaction, repose, 
or even retreat from the activities of others. 
Persons from two long separated disciplines have 
the opportunity of contributing to an understand- 
ing of what such a compromise might be. They 
are ecologists and psychologists. In either case 
they must deal experimentally with groups which 
at the upper level approach a population. By 
a population I mean a group which has reproduc- 
tive continuity through several generations, and 
where there is the opportunity for learned be- 
haviors or culture from one generation to affect 
the succeeding one. The ecologist must become 
familiar with the concepts and techniques of the 
psychologist. The psychologist must learn from 
the ecologist that the experimental animal is not 
just a machine to manipulate without regard to 
the fact that its heredity governs the expression of 
many behavior patterns, preference for particular 
characteristics of the habitat, and ability or proba- 
bility of participating in specific social relations. 
Thus, if an experimental approach to population 
dynamics and social organization on the vertebrate 
level is to develop, it requires a coalescent disci- 
pline, ecopsychology. To the extent that my 
study of the life history of the Norway rat may 
stimulate further and more experimentally oriented 
studies of vertebrate population dynamics will I 
feel satisfaction in accomplishment. 
I have not been alone in my concern with the 
characteristics of space, its utilization through 
time, and the need for more experimentally ori- 
ented comparative investigations which include 
function of the individual in the context of others 
of its species. Hediger ( 99 ) has ably marshaled 
much circumstantial evidence of such bonds 
between the organism and its environment. He 
particularly emphasizes the principle of psychic 
inertia which binds the individual to learned or 
hereditarily determined tropistic relations to its 
physical and social environment. This empathy 
with the environment he designates as the archetope 
or psychic characterization of the environment by 
the individual. Disruptions in the archetope 
resulting from displacement or changes in the 
environment lead to nostalgia, homesickness, and 
malfunction of physiology and behavior. Donald 
O. Hebb of McGill University in a seminar at the 
National Institute of Mental Health similarly 
stressed the importance of this area, which he 
designated as “homesickness” and the lack of 
experimental studies relating to it. 
References 
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thiocarbamide taste thresholds of rats and human 
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Napthyl Thio-urea (ANTU) as a rat poison. J. 
Amer. Med. Assoc. 129: 927-931 (1945). 
(3) Emlen, J. T., Jr.: Baltimore community rat control 
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(1947). 
(4) Emlen, J. T., Jr., Stokes, A. W., and Winsor, C. P.: 
The rate of recovery of decimated populations of 
brown rats in nature. Ecology 29: 133-145 (1948). 
(5) Calhoun, J. B.: Mortality and movement of brown 
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(6) Davis, D. E. : The role of intraspecific competition in 
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