Youth Ends At Age 27

Professor Timothy Salthouse of the University of Virginia found reasoning, spatial visualisation and speed of thought all decline at age of about 27. [2]

A study of 2,000 men and women aged 18 to 60 over a seven year period found "our mental abilities begin to decline from the age of 27, after reaching a peak at 22." The people involved, mostly in good health and well-educated, had to solve visual puzzles, recall words and story details and spot patterns in letters and symbols. [1]

Things like memory stayed intact until the age of 37, in general, while abilities based on accumulated knowledge, such as performance on tests of vocabulary or general information, increased until the age of 60. [2]

[2] Old Age Begins at 27, Study Finds FOXNews.com March 16, 2009.
[1] Brain decline' begins at age 27, BBC News.com March 16, 2009