Pavlov showed that learning of simple responses to 

 environmental stimuli involved a similar kind of mecha- 

 nism, but that here there was a process of storage of informa- 

 tion in the brain. When a dog smells food, there is a release 

 of saliva in its mouth in anticipation of eating, and the great- 

 er its hungriness, the more saliva is released. If, at the same 

 time that food is presented to the dog, a bell is sounded, 

 the animal starts to associate the bell with food, and 

 after a number of repititions of this process with the bell 

 preceding the food by steadily longer intervals, the dog 

 will salivate upon hearing the bell alone, even if no food 

 is finally presented. Pavlov called this learning mechanism 

 a conditioned reflex, and suggested that it comprised 

 the following stages: (a) A simple reflex action — pres- 

 entation of food causing the dog to smell, with resulting 

 salivation; (b) the simultaneous nervous impulses caused 

 by the stimuli of smell from the food and sound from 

 the bell, passed across neighboring parts of the lower brain 

 at some point in their passage to salivary gland muscles, 

 and sound memory storage region in the higher brain, 

 respectively: as a result, the nervous impulses in one circuit 

 were able to affect those in the other, since nerves are not 

 perfectly insulated from one another; (c) the two pre- 

 viously independent nerve circuits eventually became inter- 

 connected upon repeated stimulation, so that an impulse 

 originating in the ear, due to sound from the bell, was 

 transferred into nerves leading to the salivary gland mus- 

 cles, producing salivation. This process of conditioning 

 plays an important part in providing new responses in 

 animals (including ourselves) as the changed environ- 

 ment requires. The conditioned reflex is entirely at the 

 subconscious level of the brain however. 



In animals there is little mental action at any higher 



60 



