Organisational development (OD) aims to increase organizational effectiveness and health through planned interventions using behavioural science knowledge. It focuses on organizational culture and processes, encouraging collaboration between leaders and members to manage these. Major topics of OD include diagnosing organizational health and performance, and an organization's ability to adapt to change through applying organizational behaviour theory and recognizing social processes within the organization. OD is based on assumptions that higher performance is possible through well-functioning human systems, and that organizations must be adaptive. It values humanistic, optimistic, and democratic principles.