Final answer:
Most adults reach their peak of intellectual ability in early adulthood, which spans from approximately 20 to the mid-30s. Crystallized intelligence remains stable or improves during this time, while fluid intelligence begins to decline in late adulthood. Maintaining an active lifestyle can help delay cognitive decline.
Step-by-step explanation:
Most adults reach their peak of intellectual ability during early adulthood, defined as the period from around 20 to the mid-30s. During this stage, crystallized intelligence, which includes the information, skills, and strategies accumulated through experience, remains stable or even improves. Notably, intelligence test scores tend to be stable or increase until the mid-30s to mid-50s. Conversely, fluid intelligence, which involves information processing abilities, reasoning, and memory, may start to decline in late adulthood.
Despite potential declines in certain areas of cognitive functioning in later years, engaging in mental and physical activities can help delay cognitive decline. Adults who maintain an active lifestyle, both mentally and physically, tend to experience less cognitive decline and have a reduced incidence of mild cognitive impairment and dementia.