The structure of human intelligence: It is verbal, perceptual, and image rotation (VPR), not fluid and crystallized

In a heterogeneous sample of 436 adult individuals who completed 42 mental ability tests, we evaluated the relative statistical performance of three major psychometric models of human intelligence—the Cattell–Horn fluid-crystallized model, Vernon's verbal–perceptual model, and Carroll's three-strata model. The verbal–perceptual model fit significantly better than the other two. We improved it by adding memory and higher-order image rotation factors. The results provide evidence for a four-stratum model with a g factor and three third-stratum factors. The model is consistent with the idea of coordination of function across brain regions and with the known importance of brain laterality in intellectual performance. We argue that this model is theoretically superior to the fluid-crystallized model and highlight the importance of image rotation in human intellectual function.