John Adams is best known for which theoretical concept?

John Adams is best known for the Equity Theory, which focuses on the principle of fairness in social exchange relationships. This theory posits that individuals assess the fairness of their input-outcome ratios in comparison to others and that perceived inequities can lead to various emotions and behaviors. For instance, if one feels they are putting in significant effort and not receiving an equivalent outcome compared to peers, it may result in feelings of resentment or decreased motivation. Adams’ Equity Theory highlights the importance of perceived equity in job satisfaction and motivation, making it a foundational concept in understanding workplace dynamics.

The other theories listed -- Motivation-Hygiene Theory, Hierarchy of Needs Theory, and Expectancy Theory -- while significant in the fields of psychology and management, do not specifically relate to Adams and his work on equity in social contexts. Each of those theories has different focal points: the Motivation-Hygiene Theory by Frederick Herzberg deals with factors that contribute to job satisfaction and dissatisfaction; the Hierarchy of Needs Theory by Abraham Maslow outlines a progression of human needs from basic physiological needs to self-actualization; and the Expectancy Theory emphasizes individuals' beliefs about their capabilities to achieve desired outcomes.