Doggonit Ivan Pavlov, a Russian physiologist, was originally researching the role of salivation on digestion in dogs. He would present various foods and non-food objects to the dogs, then record the rate and amount of saliva produced. The responses to food by salivating are known as a reflex: a response that occurs automatically to a specific stimulus without conscious control or learning. But after a while, Pavlov noticed something odd. The dogs began to salivate without any food or food odor present. This suggested that their experiences in the lab altered the reflexive action of the salivary glands. Pavlov then observed that these responses occurring were related to certain signals that normally would not warrant a response, such as footsteps coming closer, or a human that previously presented food. Pavlov theorized that there must be two types of reflexes. The first is an Unconditioned Reflex, which is inborn and automatic, requires no learning and is generally the same for
all members of the species. The second is a Conditioned Reflex, which is acquired through experience and learning, and may vary greatly from each individual member of the species. Unconditioned Reflexes are formed by and Unconditioned Stimuli (UCS) producing an Unconditioned Response (UCR). In Pavlov’s study, the UCS was the food and the UCR was salivation. Conditioned Reflexes consist of a Conditioned Stimuli (CS), such as footsteps, producing a Conditioned Response
(CR). Pavlov had one question in mind: Exactly how were the conditioned responses acquired? He then proposed that if a particular stimulus was present in a dog’s environment and was often paired with being fed, the stimulus would become associated with food in the dog’s brain. However, prior to being paired with the food, the environmental stimulus
did not produce any important response therefore it’s called a Neutral Stimulus (NS). His first test was the pairing of a metronome and immediately after, the presentation of food. After a while, the dogs began to salivate to the sound of the metronome. The metronome had become a CS for the CR of salivation. Next, he paired the odor of Vanilla (NS) prior to a mild acid solution (lemon juice, which caused heavy salivation) being placed in the dogs mouth. After 20 repetitions, the Vanilla alone would produce salivation. Finally, as a visual test, an object would begin to rotate in front of the dog prior to the presentation of food. After only 5 pairings, the rotating object itself (CS) caused the dog’s to salivate (CR). An important finding, however, was if the NS was presented after the food, no response takes place. All of these experiments are now known as classical conditioning. Classical conditioning helped psychology launch as a true science.