Inspection time in the structure of cognitive abilities: Where does IT fit?

Inspection time (IT) correlates with IQ. This study had four aims: to locate IT within a hierarchical model of cognitive abilities; to test if IT has properties not tapped by other backward masking tasks; to test whether decision time (DT) from ‘odd-man-out’ (OMO) reaction time (RT) measures the same basic process as IT; and to test whether Wechsler performance IQ (PIQ) measures fluid ability (Gf). A battery of psychometric and chronometric tests was administered to 90 adults. Exploratory factor analysis showed that IT loaded on a general speediness factor and a higher-order general ability factor (G) but not on Gf. The results were similar for an alphanumeric pattern backward masking task suggesting that IT does not have special status as a backward masking task. DT and IT measured different processes and PIQ did not measure Gf. Confirmatory factor analyses compared results across alternative models of cognitive abilities but without differentiating one above the others. We conclude that IT does not measure fluid ability, but the question of whether information-processing speed is common to all cognitive abilities is still open.