Man: A Course of Study, usually known by the acronym MACOS or M.A.C.O.S., was an American humanities teaching program, initially designed for middle school and upper elementary grades, and popular in America and Britain in the 1970s. It was based on the theories of Jerome Bruner, particularly his concept of the "spiral curriculum". This suggested that a concept might be taught repeatedly within a curriculum, but at a number of levels, each level being more complex than the first. The process of repetition would thus enable the child to absorb more complex ideas easily.