Positivism and the rise of scientific method had a strong influence on the emerging field of education in the early 20th century. In particular, the discipline of psychology had an impact on education because psychology studied human behavior and had already established empirical research methods based on a positivist framework. Behaviorist learning theory focuses on that which is observable: how people behave and especially how to change or elicit particular behaviors. In the early 20th century, behaviorism introduced a theory of learning that was empirical, observable and measurable. The development of behaviorism is associated with many scientists, but most famously with the Russian physiologist, Ivan Pavlov, who is considered the intellectual founder of behaviorist learning theory. Many psychology researchers expressed interest in Pavlov's ideas, and as his research shifted to human behavior, other researchers also contributed their ideas on human psychology and learning theory to build a school of thought.