classical conditioning

In the 1890's, a Russian physiologist named Ivan Pavlov did some really famous experiments on dogs.He showed dogs some food and rang a bell at the same time.After a while, the dogs would associate the bell with the food.They would learn that when they heard the bell,they would get fed.Eventually, just ringing the bell made the dogs salivate.They learned to expect food at the sound of a bell.You see, under normal conditions,the sight and smell of food causes a dog to salivate.We call the food an unconditioned stimulus,and we call salivation the unconditioned response.