Which statement correctly describes intelligence stability with age?

• A. Intelligence is fairly stable with a slight decline around age 65, mainly in fluid intelligence.
• B. Intelligence varies wildly and is unstable after childhood.
• C. Intelligence increases steadily after early adulthood.
• D. Intelligence is entirely determined by environment and changes with schooling.

Answer: (A)

Intelligence tends to stay fairly stable across adulthood, with differences between individuals remaining relatively constant over time. What does change is the mix of abilities: the speed and novel problem-solving skills, called fluid intelligence, tend to decline gradually starting in midlife and become more noticeable around the mid to late 60s. Meanwhile crystallized intelligence—vocabulary and general knowledge—stays stable and can even improve with experience. So the description that intelligence is fairly stable with a slight decline around age 65, mainly in fluid intelligence, fits what research shows about aging and cognitive abilities. The other statements aren’t as accurate: intelligence isn’t wildly unstable after childhood, it doesn’t steadily increase after early adulthood, and it isn’t determined entirely by environment or schooling.