aging and intelligence

n. The relationship between performance on tests of ability and chronological age through adulthood. Generally speaking, speeded tests find a decrement in intelligence after middle school, while power tests find a slow increase throughout adulthood until physical ailments begin to interfere with performance. In practice cross-sectional studies of intelligence across age groups have found a downward trend in intelligence scores after early middle age, while longitudinal studies have found an upward trend until physical illness affects individuals. Fluid intelligence decreases with age, whereas crystallized intelligence (accumulated knowledge and skills, language) rises slowly or stays the same after middle age.