The contribution of preattentive processes to the cognitive speed-ability relationship was investigated in a sample of 80 participants. Preattentive processes were activated by presenting stimuli outside the focus of attention. The participants completed three reaction time tasks, each of which included several treatment levels, the Wechsler Adult Intelligence Scale-Revised (WAIS-R), and a measure of fluid intelligence. In order to carry out a comprehensive investigation, both ability-related variances and correlations were computed. The results revealed an increase in ability-related variances due to the stimulation of preattentive processes, whereas the size of the correlations remained constant. A comparison of ability-related variances for preattentive and focal-attentive processes showed a higher relative increase for the former and a higher absolute increase for the latter. The coefficients obtained for a structural equation model indicated that preattentive processes exerted a stronger effect on cognitive ability than focal-attentive processes.