,88 



Why Living Things Behave As They Do unit v 



Fig. 270 Lear?img includes j?mch 

 that is not written in textbooks. 

 Many neurons are brought into 

 action while this young lady 

 learns to skate, (press associa- 

 tion) 



activities of your life which are not 

 simple reflexes or instinctive acts are 

 learned acts; they are dependent on 

 learning. They make up the greater part 

 of your behavior. 



Let us study some of your learned be- 

 havior more closely. You must remem- 

 ber that much of this behavior is not yet 

 understood, that the discussion must be 

 short in this book, and that the little you 

 learn now is just a small step on the road 

 toward more complete understanding of 

 the behavior of human beings. 



The conditioned response. Let us ex- 

 amine first a simple form of learning 

 found in many animals and in very 

 young babies. You know that the pres- 

 ence of food in the mouth stimulates the 

 secretion of saliva. This response is in- 

 born; it is a true reflex. As the baby 

 grows older it learns to recognize the 

 odor or sight of certain foods. After a 

 while the odor or sioht of these foods 

 calls forth the secretion of saliva long 

 before the food reaches the mouth. A 



new stimulus (obtained through the eyes 

 or nose) now calls forth an act that at 

 first was a response to another stimulus. 

 Since the act is now a response to a dif- 

 ferent stimulus it is called a learned or 

 acquired response. It is also called a C07i- 

 ditiojied response. Sometimes it is called 

 a coiiditiofied reflex but since by defi- 

 nition a reflex is unlearned, it seems con- 

 fusing to use such contradictory words 

 together. This conditioned response is 

 one example of simple learned behavior, 

 behavior that is not reflex. 



Pavlov's experiments. More than half 

 a century ago Pavlov, the great Russian 

 physiologist, became interested in such 

 learned responses and determined to 

 study them experimentallv in animals. 

 You have read in an earlier chapter how, 

 bv placing food in the dog's mouth and 

 ringing a bell at the same time, after a 

 number of repetitions, secretion of saliva 

 took place at the sound of the bell, with- 

 out the presence of food. Pavlov substi- 

 tuted the ringing of a bell for the normal 



