Leader-Member Exchange (LMX) theory proposes that leaders form different quality relationships with each subordinate, ranging from high-quality exchanges with an "in-group" to lower-quality exchanges with an "out-group." Early research found that in-group members receive more support and responsibilities. Later studies showed high-quality LMX relationships result in better job attitudes and performance. LMX theory describes leadership as developing through three phases - stranger, acquaintance, and mature partnership - moving from lower- to higher-quality exchanges over time. The theory focuses on the dyadic relationship between each leader and member.