Research shows that bigger brains or brain regions correlate with higher Intelligence Quotient (IQ) scores in humans (e.g. Reiss, et al., 1996; Colom, et al., 2006 ).  It is easy to infer that smaller brains therefore correlate with lower IQ scores.  It is easy to further infer that IQ scores correlate with intelligence, which correlates with some vaguely defined function of fitness or success.  Then it is a simple matter to apply the transitive property and jump from bigger brains to final success.  As ever, there has been controversy about this line of thinking.

The initial purpose of the traditional Binet-Simon IQ test was to diagnose mental retardation in 1905 France (Siegler & Alibali, 2005).  Later versions, including the Stanford-Binet IQ test, expanded the purpose to proactively determine if a school-age child were likely to require more assistance in an institutional classroom setting with peers.  The IQ tests are binary filters, not linear intelligence scales and not apparently intended for adult, post-institutional educational use.  Very few job applications require an IQ test or IQ test scores. 

IQ scores then were intended to only show whether the recipient has sufficient mental capability to prevent disrupting an institution of peers in a learning scenario with relatively high student:teacher ratios of at least above 1.  That specific mental capability is the capability to perform as a student in a standardized school.  Standardized schools take as their original goals the mastery of the three R’s: “reading, ‘riting, and ‘rithmetic…” (Bailey history texts, referencing perhaps an 1818 Lady’s Magazine entry).  This would be in preparation for functional interactions in adulthood and further development of unspecified career skills of choice.  It is doubtful any superintendent would believe graduation through the basic institutional school system would finalize the student’s training for any career, let alone every career. 

For bigger brains to imply higher IQ scores to imply higher intelligence to imply anything meaningful at all needs to rely on the reader to assume and make an unsubstantiated inference that higher intelligence is definable and of substantial utility.  Research shows that bigger brains or brain regions correlate significantly with higher IQ scores.  This means that the IQ score is a good indicator of brain size in addition to its stated goal of predicting disruptions in institutional schools.  It may take a form of intelligence to prevent disrupting the class at school, but is this intelligence of any meaningful value afterwards? 

To define value, one can take the distributed, democratic “vote with the wallets” approach and examine salary and compensation data as a proxy for how much others are willing to trade for a set of goods and services.  If one examines the highest paid jobs – e.g. averages or top of the range depending on the desired design – one might for example find actors and entertainers at the top.  Or perhaps Fortune 500 CEOs.  Then measure their brain sizes and compare along the compensation scale and analyze if brain size has any measurable impact.  Finally, one must discount any confounding factors, such as genetics in brain size vs. family name recognition allowing dynasties of actors or CEOs.  

Until then, alongside research showing brain size correlates positively with IQ scores, one might also consider how the equally important and related heart size correlates with health and mortality scores.  Is a larger heart a good sign or not?  Is the answer consistent with the ultimate answer for a larger brain? Is the mechanism of enlarging the heart consistent with the mechanism for enlarging the brain?

Until then, keep on reading, ‘riting, and ‘rithmeticking.