Psychometric intelligence correlates with reaction time in elementary cognitive tasks, as well as with performance in time discrimination and judgment tasks. It has remained unclear, however, to what extent these correlations are due to top-down mechanisms, such as attention, and bottom-up mechanisms, i.e. basic neural properties that influence…

Forty untrained mildly mentally retarded and 32 untrained nonretarded junior high school students were given eight trials of practice on a self-paced memory problem with lists of letters or words. (Author)