Inspection time and IQ: Fluid or perceptual aspects of intelligence?

Past research has found an association between inspection time (IT) and fluid intelligence using measures confounded with visual processing (e.g., Wechsler PIQ or Ravens Progressive Matrices). The present study related IT to intelligence using a measure (Woodcock–Johnson—Revised, WJ-R) that has nonconfounded factors of mental ability in order to determine whether the association is based upon fluid IQ or perceptual processes. Thirty-seven undergraduate students were given fluid, crystallized, and visual processes subtests from the Woodcock–Johnson and a visual IT task. Stepwise multiple regression and partial correlations revealed that IT was related only to fluid intelligence (range corrected correlation of −.74), supporting the notion that IT reflects some fundamental underlying aspect of intelligence such as neural processing efficiency.