Theories developed from the mid twentieth century onward that treat worker motivation, group behavior, leadership style and situational judgment, rather than formal structure alone, as central to effective management, including the human relations movement's finding that social attention affects output, motivational frameworks contrasting assumptions about worker attitude, servant leadership, expectancy-based and two-factor accounts of what motivates people at work, and contingency theory's claim that the right management approach depends on the people and situation rather than one universal rule. Belongs here: any theory whose primary concern is human motivation, leadership style, or adapting management practice to people and circumstance. Does not belong here: a theory whose primary concern is formal organizational structure with no behavioral or situational element, grouped under Classical Management Theories, or a named applied process-improvement method, grouped under Quality and Process Improvement Theories.