This influential work examines how enduring dispositions or traits affect the process of aging and shape each individual’s life course. From two well-known authorities in the field, the volume is grounded in a growing body of empirical evidence. Critically reviewing different theories of personality and adult development, the authors explain the logic behind the scientific assessment of personality, present a comprehensive model of trait structure, and examine patterns of trait stability and change after age 30, incorporating data from ongoing cross-sectional and longitudinal studies. Written in a clear, jargon-free style, this book is an ideal text for advanced students and a timely reference for researchers and clinicians.