He proposed a theory of motivation based on personality and learned needs. His theory of manifest needs claims that human motivation are a result of three manifest needs. These are the need for achievement (N-Ach), the need for power (N-Pow) and the need for affiliation (N-Affil). The importance of each need varies from individual and cultural background. For example, some individuals value achievement more than affiliation. McClelland's theory is closely related to the work of Frederick Herzberg.