Mental speed hardly changes over a lifespan. Mental speed -- the speed at which we can deal with issues requiring rapid decision-making -- does not change substantially over decades. Psychologists have come to this conclusion. They evaluated data from a large-scale online experiment with over a million participants. The findings of the new study suggest that the speed of cognitive information processing remains largely stable between the ages of 20 and 60, and only deteriorates at higher ages. Source 2u.