Arthur Brooks explains cognitive shifts after age 40

Harvard professor and happiness expert Arthur Brooks suggests a paradigm shift in how human cognitive evolution is understood during adulthood. He distinguishes between two types of intelligence: fluid intelligence and crystallized intelligence.

Fluid intelligence, which includes working memory, focus, and problem-solving abilities, tends to peak before age 40. Brooks notes that the decline of this rapid processing can lead to professional burnout in middle age, as individuals struggle to maintain the same pace they once held. This often results in frustration when people attempt to compete with the speed of younger colleagues.

However, as fluid intelligence declines, crystallized intelligence emerges and grows. This form of intelligence is based on the consolidation of experience rather than disruptive innovation or working memory. Brooks states that crystallized intelligence increases significantly through the 40s and 50s and remains high through the 60s, 70s, and 80s.