Robert Gagne was an influential educational psychologist known for his work on instructional design and the conditions of learning. He received his PhD from Brown University and worked as a professor at various universities. Gagne identified five categories of learning - verbal information, intellectual skills, cognitive strategies, attitudes, and motor skills. He also proposed nine instructional events that should be followed when designing lessons: gain attention, inform learner, recall, present content, guide learning, elicit performance, provide feedback, assess performance, and enhance retention. Gagne's work was influential in the development of instructional systems design and based on B.F. Skinner's principles of sequenced learning.