- Aristotle and others before 1879 discussed concepts relevant to modern I/O psychology like specialization of labor and leadership selection.
- Hugo Munsterberg is considered the father of industrial psychology; he pioneered applying psychological findings to practical work matters in the early 1900s.
- Frederick Taylor's scientific management philosophy in the early 1900s emphasized scientifically designing work and selecting/training best workers, which greatly impacted organizations.
- World War I saw psychologists like Robert Yerkes and Walter Dill Scott conduct testing and job placement of soldiers, advancing applied psychology.
- The landmark Hawthorne Studies in the 1920s revealed the importance of human factors like attention, attitudes, and informal groups in work productivity.