We studied developmental trends in 5 important reasoning tasks that are critical components of the operational definition of rational thinking. The tasks measured denominator neglect, belief bias, base rate sensitivity, resistance to framing, and the tendency toward otherside thinking. In addition to age, we examined 2 other individual difference domains that index cognitive sophistication: cognitive ability (intelligence and executive functioning) and thinking dispositions (actively open-minded thinking, superstitious thinking, and need for cognition). All 5 reasoning domains were consistently related to cognitive sophistication regardless of how it was indexed (age, cognitive ability, thinking dispositions). The implications of these findings for taxonomies of developmental trends in rational thinking tasks are discussed.