Answer:
The answer is Ivan Pavlov.
Explanation:
Ivan Pavlov was known for his studies in classical conditioning --that is, the way environmental stimuli can affect our physiology.
There is a very well know experiment in which he rang a bell every time he was going to feed a dog. He noticed that after the dog got conditioned to associating the sound of the bell with food, the dog would start salivating just by hearing the sound.