In general, intelligence remains high throughout most of adulthood. Although there are some cognitive declines during the aging process, these declines occur much later than originally thought, are typically more pronounced in intelligence tests requiring speed and motor skills, and can be reduced by remaining active. In addition, when discussing changes in intellectual abilities during adulthood, a distinction needs to be made between crystallized intelligence and fluid intelligence (Berg, 2000).
Crystallized intelligence comprises acquired knowledge and skills based on life experiences, whereas fluid intelligence comprises problem-solving abilities ...