RE: Comment about ‘Fractionating Human Intelligence’. Non-existent flaws in the original article and their relation to limitations of the P-FIT model

In this invited response, we first note that contrary to the claims of Haier and colleagues, they were not part of the review process for the article Fractionating Human Intelligence. We then expand on the rationale underlying the primary objective of the study, to determine whether the axes of individual differences in cognitive ability reflect the manner in which the human brain is organised into intrinsic functional networks, and contrast the resultant advance with the more limited aims and methods of the P-FIT model. We address the primary objection of Haier and colleagues by demonstrating that the unrotated model is not only a poorly defined psychological construct, but also neurobiologically implausible in the context of the fMRI data. Finally, we discuss how the distinct strengths of behavioural and neuroimaging data may best be combined in order to refine a model that captures the intrinsic architecture of human cognitive abilities.