Explain similarities and differences in cognition across age groups and gender.

Answers will vary. K. Walter Schaie sought to separate the effects of age-related changes within the individual from cohort effects (similarities among peers due to group members being about the same age). To do so, he introduced a developmental model that elevated the study of age-related changes above simple longitudinal and cross- sectional studies. He used successive repeated and independent sampling of age cohorts across the decades of a longitudinal study. The resulting data permitted many comparisons within and across age groups and birth cohorts. Using his method, Schaie found that late adolescents are likely to have the broadest general knowledge of the sciences, but young adults become more focused in their use of scientific expertise than adolescents are. Many adolescents acquire general scientific knowledge in biology, chemistry, and physics during high school. And now, more than ever, girls remain with boys and keep pace with them in these classes. The same is generally true in algebra, geometry, precalculus, and calculus.