According to John Horn, what happens to crystallized and fluid intelligence during middle age?

The correct answer highlights that during middle age, crystallized intelligence tends to increase while fluid intelligence begins to decline. Crystallized intelligence refers to the knowledge and skills that are acquired through experience, education, and culture, and it often continues to grow as individuals accumulate more experiences and knowledge throughout their lives. This can include vocabulary, general knowledge, and expertise in various areas, which often expand with age.

On the other hand, fluid intelligence, which involves the ability to think abstractly, solve problems, and process information quickly, usually reaches its peak in young adulthood and starts to decline in middle age. This decline can be attributed to various factors, including biological aging and reduced cognitive processing speed.

This differentiation is important in understanding cognitive development in adults. In summary, the increase in crystallized intelligence reflects the accumulation of knowledge over time, while the decline in fluid intelligence underscores the changes in cognitive processing abilities that occur as a person ages.