40 is the new 30, but maybe it should be the new 80.

A report from BBC says mental abilities start to dwindle at age 27, "marking the start of old age." The story refers to a study by Timothy Salthouse, University of Virginia, published as an open peer commentary manuscript in April's Neurobiology of Aging. About 2,000 subjects solved puzzles, recalled words and recognized patterns as a measure of mental agility, and in nine out of 12 tests the average age at which the top performance was achieved was 22.

The first age at which there was any marked decline was at 27 in tests of brain speed, reasoning and visual puzzle-solving ability, the BBC article reports, but things like memory stayed intact until the age of 37, on average, and abilities based on accumulated knowledge, such as performance on tests of vocabulary or general information, increased until the age of 60.

This begs the question: if reasoning starts to decline at age 27, why do you have to be 35 to be president, and why is the average age of a Supreme Court justice currently at 68? (As of January 2009, the average age of the U.S. Supreme Court justices is 68 years. If no Justices retire, the average age will reach 69 with Justice Alito's 59th birthday, on April 1, 2009.)

Volume 30, Issue 4, April 2009, Pages 507-514