Schaie's lifespan cognitive theory proposes 7 stages of adult cognitive development: 1. The acquisitive stage from childhood to adolescence focuses on acquiring knowledge for its own sake. 2. The achieving stage from ages 20-30s uses knowledge to pursue career and family goals. 3. The responsible stage from 30s-40s focuses on solving practical professional and personal situations. 4. The executive stage from 40s-50s takes a broader perspective including concerns about society and politics. 5. The reintegrative stage from 50s-60s focuses on personally meaningful tasks.