The first person to do careful scientific studies of learning was: william wundt ivan pavlov william james john watson

Ivan Pavlov
Due to his experiments, he influenced other scientists. The experiment that he is most known is: Pavlov's dogs.
Pavlov fed dogs and was looking at salivation in response to the food. At a certain point, whenever he entered the room, the dog would start to salivate even when he was not bringing them food. This it is an unconditioned response to an unconditioned stimulus.