Challenging the view that cognitive aging is identical with decline, Paul B. Baltes, Jacqui Smith, and Ursula Staudinger adopt the hypothesis of simultaneous growth and decline and relate it to wisdom. Trait psychology is discussed by Paul T. Costa, Jr., and Robert R. McCrae, who review the most recent advances and present new data from longitudinal studies. K. Warner Schaie and his colleagues describe problems and methods of studying natural cohorts within a longitudinal study and report the first data on adult parent-offspring similarity determined as a function of the age of the pair when studied. A commentary chapter by Ross A. Thompson concludes the volume.