1. Introduction. 2. The Nature and Function of Theories. 3. Development of Theories of Development. 4. The Information-Processing Framework. 5. Experience and Expertise. 6. General Methodological Issues. 7. Requirements of a Cognitive Aging Theory. 8. The Speed Factor in Cognition. 9. The Speed Factor in Cognitive Aging. 10. The Processing Rate Theory of Cognitive Aging. 11. Memory Abilities. 12. Perceptual-Spatial Abilities. 13. Reasoning Abilities. 14. Implications and Future Directions. References. Index.