Who developed theory of conditioned response?

He did an experiment on a dog in one of his labs. He noticed that when his assistant walked down the corridor with his food he would begin to salivate. So he began to ring a bell every time that the dog would get food.

• Food #=# dog salivates
• Bell ringing #=# No response off dog
• Food #+# Bell ringing #=# Dog salivates
• Bell ringing #=# Dog salivates

He found that after 6 times with the bell and food the dog would salivate to the bell. But the dog would only salivate to one bell and not the others. The dog was classically conditioned to associate the bell ringing with food.