When Pavlov trains a dog with a bell, the simultaneous appearance of the bell and food is a new environment. This new environment makes the dog establish a new neural connection. This new neural connection makes the dog establish a conditioned reflex. The dog salivates when it hear the bell, even if it don't see food. When a newly established conditioned reflex can benefit a dog, it becomes a dog's knowledge. Does the dog really understand this knowledge? The dog doesn't know the story behind the bell at all. It doesn't know what Pavlov wanted to explain through this experiment, but the association caused by the bell has become a dog's knowledge. For human, establishing a useful conditioned reflex is to add a kind of knowledge. To dogs, adding a kind of knowledge is to add a biological character. The connection between bell and food is dog's interpretation of the world.

Lower forms of animals can only establish simple conditioned reflex, advanced animals can establish complex conditioned reflex, that is, the connection between multiple phenomena and changes in interest. If the dog observes that changes in self-interest do not occur at the same time as the phenomenon A, but at the same time as the phenomenon A+B, then in the dog's nervous system, A+B will be linked to the change in the interest. This is the earliest analysis.

For example, A is a ringtone, B is a breeder, and food is only available when the ringtone and the breeder appear at the same time; if there is only a ringtone, no breeder (the ringtone may come from a visitor), there is no food, then in the nervous system of the dog, A+B will be contacted with food. If the dog continues to observe that the food does not always appear at the same time as A+B, but always at the same time as the phenomenon A+B+C, then A+B+C will be contacted with food. This is called further analysis. Induction is the process of establishing conditioned reflexes, analysis is the process of establishing complex conditioned reflex