Robert Gagne was an influential educational psychologist known for his work on conditions of learning and instructional theory. He received his PhD from Brown University in 1940 and worked as a professor at various universities. Gagne's major publications included The Conditions of Learning and Instructional Theory Foundations. He proposed a learning hierarchy consisting of different types of learning outcomes ranging from simple to complex: signal learning, stimulus-response learning, chaining, verbal association, multiple discrimination, concept learning, rule learning, and problem solving. Gagne also identified nine instructional events that should be followed to facilitate learning: gaining attention, informing learners of objectives, stimulating recall, presenting stimuli, providing guidance, eliciting performance, providing feedback, assessing performance, and