A method for measuring human intelligence using a neurobiogical model is provided. The method enables neurometric IQ to be measured by processing MRI and fMRI images of a subject to determine cortical thicknesses and brain activation level, determining structural IQ (sIQ) and functional IQ (fIQ) from the determined cortical thicknesses and brain activation level, and using the structural IQ (sIQ) and the functional IQ (fIQ) as predictors to measure the neurometric IQ of the subject. With this, individual differences in general cognitive ability can be easily assessed. It suggests that general cognitive ability can be explained by two different neural bases or traits: facilitation of neural circuits and accumulation of crystallized knowledge.