While researching the digestive system of dogs, Pavlov placed meat powder in the dogs' mouths and measured responses in various organs. He discovered that the dogs began to salivate in response to the meat powder before it was presented to them. Pavlov found this response intriguing and abandoned his research to begin studying what he later called classical conditioning.
Unconditioned responses occur naturally. These are innate reflexes such as yawning or sneezing. In the example of Pavlov's dogs, the unconditioned response is salivation. The dogs naturally salivated in response to food. The food is called an unconditioned stimulus since it triggers the naturally occurring, or unconditioned, response.
Conditioned responses do not occur naturally. They occur due to exposure and experience. Pavlov observed that after exposure to the meat powder, the dogs began salivating when they recognized cues that the meat powder was coming, such as when the researcher was preparing the meat powder or when the researcher entered the room. He experimented with this response by ringing a bell prior to presenting the food. The dogs began to salivate when he rang the bell, even when there was no food present. In this case, salivation is a conditioned response to a ringing bell because the dogs were conditioned to associate the bell with the food.
Conditioned responses can be observed everyday through an individual's responses to the environment. Fear of snakes is one example. Children are not necessarily born afraid of snakes. However, they learn to fear them when they hear parents scream when they see a snake in the yard or talk about their own fear when they see one on television. Getting good grades is another example. A child does not know an "A" on a test is good until the teacher or parents praise him for receiving one.