Robert Gagné was an educational psychologist known for his theory of conditions of learning. He identified nine events of instruction that address the different mental conditions for learning. These include gaining attention, informing learners of objectives, stimulating recall of prior knowledge, presenting new material, providing guidance, eliciting performance, providing feedback, assessing learning, and enhancing retention and transfer. Gagné's model emphasizes that learning builds from simple to complex and that instruction should account for individual differences in learners.