Many experts say mental speed peaks at age 20 and then begins to decline.

But new research in the journal Nature Human Behavior contends cerebral swiftness involves several components, one of which stays speedy until age 60.

A common measure of mental speed involves timing a basic cognitive task like comparing two letters or categorizing images.

But such tests really measure a combination of abilities: the mental encoding that stores sensory data; the decision process itself, slowed by caution; and the motor function of pressing a button.

Based on a cross-sectional study of one million people ages 10-80, the authors found the mental process of decision making per se did not start to slow down until age 60.

Slower reaction times reported elsewhere likely stemmed from declining reaction times, which peak in our teens, and greater decision caution, which increases as we age.