NEW YORK (Reuters Health) – Declining mental function is often seen as a problem of old age, but certain aspects of brain function actually begin their decline in young adulthood, a new study suggests. The study, which followed more than 2,000 healthy adults between the ages of 18 and 60, found that certain mental functions -- including measures of abstract reasoning, mental speed and puzzle-solving -- started to dull as early as age 27. Dips in memory, meanwhile, generally became apparent around age 37. On the other hand, indicators of a person's accumulated knowledge -- like performance on tests of vocabulary and general knowledge -- kept improving with age, according to findings published in the journal Neurobiology of Aging.
So according to this article, at 37 you lose memory. At 27, mental speed.
I think we can go even further back. Roll back another 10 years. What about age 17? That's when you lose the ability to remember anything your mother has told you.
Or age 7? You lose the ability to pay attention (at least in the second grade classes I'm in).