IQ and the Brain

Intuitively, as evidenced by the saying “big brains”, there is a relation between brain morphology and intelligence, at least as measured by IQ (Intelligence Quotient) tests. The better known such assessments are WAIS and WISC i.e. Wechsler Intelligence Scale for Adults and Children, respectively.

Further, Alfred Binet was the first to have thought of such operationalization, and developed an initial test to facilitate children’s scholastic placement. Criticisms of intellectual quotient results have ranged from their correlations with SES (SocioEconomic Status), bias against certain groups, to failure to predict success and occasional overlook of traits that may qualify as intelligent. Also, IQ averages in the general population follow a normal distribution.

But what do neuroscientists have to say on the topic? The present short essay attempts to answer this question by first turning to Johnson et al. (2008). Thus, applying VBM (Voxel-Based Morphometry) and comparing brain gray and white matter volumes as related to numerical results, the researchers found robust correlations. Consequently, differences in brain structure may reflect variety in sharpness, suggesting neuroanatomical underpinnings as clarification, at least for non-mathematically assessed cognitive capacities. In addition, the authors insist that their data support a previously established model (Carroll, 1993) of cognitive abilities operating on both a general and a task specific basis.

By the same token, gray as well as white matter volumes have been linked to intelligence As a brief aside, gray matter consists of neural bodies called soma, whereas white matter encompasses cellular projections, called axons. Axons are myelinated (myelin is a fatty substance speeding transmission), which is why they result in lighter color.

Along these lines, while confirming the association between cerebral architecture and IQ, Li et al. (2008) went further to investigate specific relationships. So, they write that COMT va1158met (gene variant) acts on the association between brain white matter and IQ. Their findings support the notion that COMT val158met influences quick wittiness. Hence, the work adds to the body of knowledge linking genetics to intellect dissimilarities in the general population.

Finally, regardless of how persistent are rankings of IQ scores (they do increase in most individuals overtime, but retain proportion) and high accuracy in scholastic achievement foreshadowing, other measures have been proposed as alternatives. One such illustration is EQ or Emotional Quotient.


  • Carroll, J. B. (1993). Human cognitive abilities: A survey of factoranalyticstudies. Cambridge, England: Cambridge University Press.
  • Johnson, W., Jung, R. E., Colom, R. & Haier, R. J. (2008). Cognitive abilities independent of IQ correlate with regional brain structure. Intelligence, 36: 18-28.
  • Li, J., Yu, C., Li, Y., Liu, B., Liu, Y., Shu, N., Song, M., Zhou, Y., Zhu, W., Li, K. & Jiang, T. (2008). COMT Val158Met modulates association between brain white matter architecture and IQ. American Journal of Medical Genetics: Neuropsychiatric Genetics, Part B, 150B: 375-80.

comic book woman on descartes

Cogito ergo sum is Latin for: I think, therefore I am… The phrase was coined by mathematician Rene Descartes… Illustration : Megan Jorgensen