Russian physiologist and Nobel laureate Ivan Pavlov is chiefly known for his discovery of the conditioned reflex, a reflex developed gradually by training in association with a specific repeated external stimulus. In the 1890s, he was investigating the gastric function of dogs when he noticed that the animals began salivating at the mere sound of the bell that preceded their feedings. He made this phenomenon the focus of his research. What other experimental subjects did he use in his research? Discuss