The authors read the participation research through the model: the higher a group's task-relevant readiness, the more likely participation in decisions is to work, and the lower, the less (participation at very low readiness pools ignorance, so direction works better); effectiveness rises from low to moderate readiness and then plateaus, because highly expert people often prefer the most expert member to decide. Apparent contradictions between studies (Likert's employee-centred findings in the United States against Hersey's close-supervision findings in 1960s West Africa; Coch and French against the Norwegian replication) are explained by the cultural readiness of the work force: level of education, standard of living and industrial experience. Participation meets belonging and esteem needs, but growth comes from work that offers achievement and challenge.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.