The most basic form is associative learning, i.e., making a new association between events in the environment. There are two forms of associative learning: classical conditioning (made famous by Ivan Pavlov’s experiments with dogs) and operant conditioning.
Classical Conditioning (Ivan Pavlov) physiologist, in 1903
Classical conditioning is a reflexive or automatic type of learning in which a stimulus acquires the capacity to evoke a response that was originally evoked by another stimulus. In the early twentieth century, Russian physiologist Ivan Pavlov did Nobel prize-winning work on digestion. While studying the role of saliva in dogs’ digestive processes, he stumbled upon a phenomenon he labeled “psychic reflexes.” While an accidental discovery, he had the foresight to see the importance of it. Pavlov’s dogs, restrained in an experimental chamber, were presented with meat powder and they had their saliva collected via a surgically implanted tube in their saliva glands. Over time, he noticed that his dogs who begin salivation before the meat powder was even presented, whether it was by the presence of the handler or merely by a clicking noise produced by the device that distributed the meat powder. Fascinated by this finding, Pavlov paired the meat powder with various stimuli such as the ringing of a bell. After the meat powder and bell (auditory stimulus) were presented together several times, the bell was used alone. Pavlov’s dogs, as predicted, responded by salivating to the sound of the bell (without the food). The bell began as a neutral stimulus (i.e. the bell itself did not produce the dogs’ salivation). However, by pairing the bell with the stimulus that did produce the salivation response, the bell was able to acquire the ability to trigger the salivation response. Pavlov therefore demonstrated how stimulus-response bonds (which some consider as the basic building blocks of learning) are formed. He dedicated much of the rest of his career further exploring this finding. In technical terms, the meat powder is considered an unconditioned stimulus (UCS) and the dog’s salivation is the unconditioned response (UCR). The bell is a neutral stimulus until the dog learns to associate the bell with food. Then the bell becomes a conditioned stimulus (CS) which produces the conditioned response (CR) of salivation after repeated pairings between the bell and food. Thorndike's Experiments on Cats:
Thorndike experimented on a variety of animals like cats, fishes, chicks and monkeys. His classic experiment used a hungry cat as the subject, a piece of fish as the reward, and a puzzle box as the instrument for studying trial-and-error learning. In this typical experiment, a hungry cat was placed inside the puzzle box, and a piece of fish was kept outside the box. The cat could not reach the fish unless it opened the door. In order to escape from the box, the cat had to perform a simple action as required by the experimenter. The cat had to pull a loop or press a lever in order to open the door. Once the door was opened, the cat could escape and eat the fish. What did the hungry cat do inside Thorndike's puzzle box? Initially it made random movements and ineffective responses. On the first trial, the cat struggled valiantly; it clawed at the bars, it bit; it thrust its paws out through any opening; it squeezed itself through the bars; it struck out in all directions. All the irrelevant responses continued for several minutes until the cat hit upon the correct response, by chance. Accidentally, it pulled the loop and the door opened. The cat came out of the box and was allowed to take a small part of the fish. It was then put inside the puzzle box for the second trial. In the second trial, the time taken to pull the loop reduced a bit. Every time the cat came out of the box and took a piece of fish, Thorndike put the cat inside the box again. Thorndike and the cat kept up this exercise for a...