The correct answer is letter D
Associative implicit memory can also be divided into two fundamental types: classical conditioning and operant conditioning. The first is related to learning the relationship between two stimuli, while the second concerns the relationship between a stimulus and an animal's behavior.
Classical conditioning is also known as Pavlovian conditioning, because it was first studied by Russian physiologist Ivan Pavlov in the late 19th century. Pavlov was studying the salivation of dogs, when he noticed something curious: dogs were able to “guess” that food was coming. For example, when dogs heard Pavlov's footsteps, they already knew that they would be offered food next, so they started salivating without having seen the food. Pavlov then assumed that the dogs had memorized an association between two distinct (but related) events. Then Pavlov went on to test this idea, using an unrelated stimulus. The essence of classical conditioning therefore involves the existence of a conditioned stimulus and an unconditioned stimulus, in which the first serves as a "clue" to the second, although it is not necessarily related to the behavior it will evoke. The second stimulus is also called "reinforcement", being in the laboratory typically "represented" by food or electric shocks. It is called “unconditioned” because it gives rise to an animal's innate response to the stimulus. (Dogs' salivation before food is innate, for example.)
