For the average individual in late adulthood, traditional tests of intelligence demonstrate that

cognitive abilities decline

Explanation:

Cognitive abilities refers to the brain's general ability to process, encode, store, and retrieve the information that it receive.

As people reach their late adulthood (when they surpass the age of 60) , our cells ability to regenerate started to decline, this include the cells in our brain which is responsible in controlling all of these cognitive abilities.  Because of this, people in late adulthood tend to have lower scores during traditional tests compared to their younger self.