This document discusses adult stages of development and how they relate to leadership effectiveness. It outlines several theories that divide adults into stages based on factors like their ability to handle complexity, accept feedback, solve problems, and manage conflict. The majority (80%) are considered conventional thinkers at the Expert and Achiever stages. These stages are focused on goals, outcomes and establishing credibility through expertise. Later post-conventional stages like Catalyst and Co-Creator can better respond to change, think strategically and effect system-wide change. The document provides examples of how to interact with individuals at different stages and potential challenges they may face.