Mental powers start to diminish at 27 after peaking at 22, marking the start of old age, US research suggests.
Professor Timothy Salthouse of the University of Virginia found reasoning, spatial visualization and speed of thought all decline in our late 20s.
The Professor's study lasted seven years and and was based on 2,000 healthy people aged 18-60 as is published in the journal Neurobiology of Aging.
In 9 out of 12 tests the average age at which the top performance was achieved was 22. The first age at which there was any noticeable decline was at 27 in tests of brain speed, reasoning and visual puzzle-solving ability.
Memory abilities stayed intact until the age of 37, on average. Abilities based on accumulated knowledge, such as performance on tests of vocabulary or general information, increased until the age of 60.