Longitudinal studies show that intelligence scores ______.

A) peaks in early adulthood, declines through middle adulthood, and drops steeply in late adulthood
B) vary by gender with males showing greater declines over time than females
C) increase into middle adulthood, especially on tests that reflect accumulated knowledge
D) vary by gender with females showing greater declines over time than males

Longitudinal studies consistently show that intelligence scores increase into middle adulthood, with peak performance occurring in the late 30s or early 40s. This increase is especially apparent on tests that reflect accumulated knowledge and abilities rather than speed or abstract reasoning. Scores on tests of fluid intelligence, such as working memory capacity, decrease somewhat in middle adulthood but usually not to the extent suggested by cross-sectional comparisons. There is little evidence that intelligence scores drop sharply in late adulthood. Gender differences in changes in intelligence scores over time are small and inconsistent.