Frederick Herzberg was an American psychologist known for introducing job enrichment and developing the two-factor theory of motivation. The two-factor theory states that job satisfaction and dissatisfaction are influenced by separate sets of factors - motivators related to the work itself that can increase job satisfaction, and hygiene factors related to the work environment and context that do not increase satisfaction but can cause dissatisfaction if absent. Herzberg tested this theory by interviewing accountants and engineers about times they felt exceptionally good or bad at work. The theory suggests managers should focus on motivators like achievement, recognition, and responsibility to improve attitudes and productivity.