Herzberg investigated American white-collar workers to discover what motivates them. He found that job satisfaction and dissatisfaction are influenced by separate factors. Motivation factors like achievement, recognition, and responsibility can motivate employees, but only if hygiene factors like pay, supervision, and working conditions are also satisfactory and not sources of dissatisfaction. Herzberg argued that managers must ensure both factors are addressed to improve motivation and reduce dissatisfaction among employees. Critics argue Herzberg's theory did not consider the importance of group work and only studied professional occupations.