is a type of learning in which a neutral stimulus comes to bring about a response after it is paired with a stimulus that naturally brings about that response.

Classical conditioning                                                  

Explanation:

Classical conditioning: In psychology, the term "classical conditioning" is described as one of the different learning theories which was introduced by Ivan Pavlov while working with dogs.

Classical conditioning is also classified as respondent conditioning or Pavlovian conditioning and is defined as a process through which a biologically existing stimulus is being paired or associated with a formerly unlearned or neutral stimulus.

In the question above, the given statement signifies the classical conditioning theory.

fertile good for trade etc