IQ does not correlate with the number of brain cells in the human neocortex and was only weakly correlated to brain weight or the volume of key areas in the gray & white matter and of the cerebral ventricles

Is There a Correlation Between the Number of Brain Cells and IQ? Nicharatch Songthawornpong, Thomas W Teasdale, Mikkel V Olesen, Bente Pakkenberg. Cerebral Cortex, bhaa249, September 16 2020. https://doi.org/10.1093/cercor/bhaa249

Abstract: Our access to a unique material of postmortem brains obtained from decades of data collection enabled a stereological analysis of the neuron numbers and correlation of results with individual premorbid intelligence quotient (IQ) data. In our sample of 50 brains from men, we find that IQ does not correlate with the number of brain cells in the human neocortex and was only weakly correlated to brain weight. Our stereological examination extended to measures of several other parameters that might be of relevance to intelligence, including numbers of cerebral glial cells (astrocytes, oligodendrocytes, and microglia) and the volume of key areas in the gray and white matter and of the cerebral ventricles, also showing near-zero nonsignificant correlations to IQ.

Keywords: Børge Priens Prøve (BPP), cell numbers, human brain, intelligence quotient, stereology