CHAPTER VI 
Laws AND HYPOTHESES FOR BEHAVIOR 
Laws OF BEHAVIOR IN GENERAL 
\ Behavior is predictable. The first law of behavior, one 
fraction of the general law of the uniformity of nature, is 
that with life and mind, as with mass and motion, the same 
cause will produce the same effect, — that the same situa- 
tion will, in the same animal, produce the same response, — 
and that if the same situation produces on two occasions two 
different responses, the animal must have changed. 
[Scientific students of behavior will, with few exceptions, 
accept this law in theory, but in practice we have not ‘fully 
used it. We have too often been content to say that a man 
may respond in any one of several ways to the same situa- 
tion, or may attend to one rather than another feature of 
the same object, without insisting that the man must in each 
case be different, and without searching for the differences 
in him which cause the different reactions. | 
The changes in an organism which make it respond differ- 
ently on different occasions to the same situation range from 
temporary to permanent changes. Hunger, fatigue, sleep, 
and certain diseases on the one hand, and learning, immu- 
nity, growth and senility on the other, illustrate this range. 
Behavior is predictable without recourse to magical agen- 
cies. It is, of course, the case that any given difference 
between the responses of an animal to the same situation 
B33 241 
