, Ivan Petrovich 1849-1936.
Russian physiologist who studied the digestive system of dogs, investigating the nervous control of salivation and the role of enzymes. His experiments showed that if a bell is rung whenever food is presented to a dog, the dog will eventually salivate when it hears the bell, even if no food is presented. This demonstration of what is known as a conditioned response prompted later scientific studies of human and animal behavior.