Final answer:
Age can be an indicator of intellectual abilities and behavior, with IQ scores used for intelligence measurement. Cognitive decline starts in late adulthood, with fluid intelligence declining while crystallized intelligence holds steady or improves. However, individual differences should be considered.
Step-by-step explanation:
A good age indicator of intellectual abilities and behavior depends on the specific cognitive aspect being considered. For intelligence, IQ scores are often used as a measure.
The majority of people have an IQ score between 85 and 115, and only 2.2% of the population has an IQ score below 70. A person who earns a score approximately two standard deviations below the mean on an intelligence test, has major deficits in adaptive functioning, and if these cognitive and adaptive deficits were present before the age of 18, they could be diagnosed as having an intellectual disability (ID).
On the other hand, the age at which cognitive decline starts to occur varies. Our cognitive abilities remain steady throughout early and middle adulthood, with crystallized intelligence tending to hold steady or improve as we age. However, in late adulthood, there is a decline in fluid intelligence, which includes information-processing abilities, reasoning, and memory.
Overall, age can be an indicator of intellectual abilities and behavior, but it is important to consider specific cognitive aspects and individual differences as well.