Need theory, also known as three needs theory, is a motivational model and management tool proposed by psychologist David McClelland, which attempts to explain how the needs for achievement, affiliation, and power affect the actions of people. The model was developed in the 1960s, two decades after Maslow's hierarchy of needs was first proposed in the early 1940s. McClelland stated that every person has these three types of motivation regardless of age, sex, race, or culture. The type of motivation by which each individual is driven derives from their life experiences and the opinions of their culture. This need theory is often taught in classes concerning management or organizational behaviour.