Processing speed in the Hick task is a better indicator of intelligence when assessed as inspection time

Processing speed (PS) is modestly associated with intelligence and frequently measured as inspection time (IT; time needed to discriminate two stimuli). Other PS measures are simple and choice reaction times (RTs) as assessed in different conditions of the Hick task. RTs in the Hick task are less strongly related to intelligence than IT, probably due to motor-related processes. We investigated whether PS in the Hick task is more strongly related to intelligence when assessed as IT rather than RT. Ninety-six subjects completed Cattell’s Culture-Fair-Test and performed on a classic Hick task version and an adaptive version (stimulus presentation time adaptively varied to the 75%-difference threshold). IT in the adaptive version correlated more strongly with intelligence, r=-.53, p<.01, than RT in the non-adaptive condition, r=-.26, p<.05, indicating that IT is the better indicator of intelligence than RT even when derived from very similar task conditions.