BEHAVIORISTIC STUDY OF THE RAT 
3 
ing factors are rarely definitely known and controlled. Because 
of these difficulties recourse must be had for the present to study 
of the behavior of animals, where the life situations are after all 
very much less complicated, and where the activities and react¬ 
ions may be changed and distorted at will under controlled 
conditions. 
It is largely for the solution of problems of this nature that 
animal psychology must be looked to for help in the future. 
Work in this field is at present at a very low ebb, chiefly for the 
reason that investigators have limited their interests almost 
completely to the study of the part reactions of animals (reac¬ 
tions to lights, colors, sounds, learning problems) and have en¬ 
tirely neglected the broader biological aspects of the lives of 
animals. 
The work presented in the following pages represents an 
attempt to attack these problems from the angle of the life and 
responses of the whole organism. The attack is made on the 
most easily approachable and least difficult points. It includes 
only a small part of the total behavior problem, the study of gross 
bodily activity before it has become specifically connected with 
any of the many complicated features of the environment. The 
relation of this activity to certain vital factors of the environ¬ 
ment, food, temperature, illumination is first examined. This is 
followed by an examination of the origin of the activity, what it 
is that causes the animal's activity. Finally the relation of this 
diffuse undirected activity to one of the animal’s most important 
specific responses, its food-seeking activity (hunger reaction), 
is examined. 
In making this study of the gross bodily activity of the rat the 
emphasis is laid throughout on what the animals do of their own 
accord, free from all external stimulation. For after all, there is 
a marked difference however not well recognized, between what 
an organism can be made to do and what it does of its own account 
(internal stimuli). The emphasis is usually placed on the former, 
that is on the training element—this is true particularly in the 
whole field of education probably even more so than in the field 
of animal psychology. Interest has only recently begun to 
