Robert Gagné was an educational psychologist known for his theory of instruction called the "Conditions of Learning". The theory outlines five categories of learning and eight types of learning that require different instructional conditions. Gagné believed that learning progresses from simple to complex and that each type of learning builds on lower levels. The theory provides guidelines for instructors to gain attention, present objectives, stimulate recall, provide guidance, elicit performance, and assess learning. However, the theory has been criticized for not accounting for self-learning or discovery-based learning.