The present investigation was carried out to see whether the relationship between the indices of reaction time (RT) and intelligence (both G(f) and G(c)) varies as a function of person (age x sex) and task variables (sensory modality, i.e. visual and auditory RT and three levels of task complexity, i.e. SRT, 2-CRT and 3-CRT). RT indices, Raven's Standard Progressive Matrices and Wechsler's Digit Span Task scores were collected on 50 males (from 3 age groups: 20-30, 50-60 and 60-80 years) and 40 females (from 2 age groups: 20-30 and 50-65 years). The intercorrelation matrix revealed that correlations between RT indices, intelligence and Digit Span Task were in the expected direction. Furthermore, it was found that task variables moderate intelligence- and Digit Span Task-RT relationships to a greater extent than person variables such as age and sex.