This section discusses theories of training and learning, focusing on three domains: cognitive, affective, and psychomotor skills. It explains that in the 20th century, learning came to be seen as more complex than a simple transaction, with the role of instructors as important to student success. Researchers discovered multiple dimensions of learning, requiring different instruction methods. The domains are broad categories of learning types. Cognitive learning requires internalizing facts and information, and training stresses improving thinking and arranging learning effectively. Memory involves short-term, long-term, and sensory memory.