Response speeds in simple decision-making tasks begin to decline from early and middle adulthood. However, response times are not pure measures of mental speed but instead represent the sum of multiple processes.
Applying the model to cross-sectional data from 1.2 million participants to examine age differences in cognitive parameters, results indicate that response time slowing begins as early as age 20, but this slowing was attributable to increases in decision caution and to slower non-decisional processes, rather than to differences in mental speed.
Slowing of mental speed was observed only after approximately age 60. This research thus challenges widespread beliefs about the relationship between age and mental speed.
Using data from over one million people, von Krause et al. show that mental speed in a decision task remains steady up to age 60, and that slowing response times before this age are due to decision caution and non-decision processes.