Does Size REALLY Matter??

Posted by Curt Kinghorn on Oct 14, 2016 7:16:47 PM

Does Size REALLY Matter?

Brain size, of course!  What did you think I was talking about??

Humans are generally regarded (by humans!) to be the most intelligent species on earth.  (There is good-natured disagreement on this by Douglas Adams, author of The Hitchhiker’s Guide to the Galaxy series.  In these books, humans are the 3rd most intelligent creatures following below dolphins with white mice as the most intelligent.  How can mice be the most intelligent??  It is because they are pan-dimensional beings who are manifest as “white mice” in our measly 4-dimensional world (ala the book Flatland, a book that influenced Einstein!). You can’t consider yourself fully educated unless you have read The Hitchhiker’s Guide!  But, I digress!) 

Hitchhikers_Guide.jpgFlatland.jpg

One reason humans are so smart is that humans have pretty big brains!  But, other species have bigger brains than humans.  Shown below is a chart put together with data from Robust Regression and Outlier Detection (P.J. Rousseeuw & A. M. Leroy, 1987 Wiley, p. 57) where I added sperm whale and Neanderthal data.  As can be seen, the sperm whale has a brain that weighs approximately 17 pounds and an elephant brain is about 13 pounds compared to the human brain of about 3 pounds!  Humans don’t even have the largest brain for hominids.  That title goes to the Neanderthal at about 3.1 pounds.  So, why are humans so much smarter than other animals with larger brains?

 

Brain_Size.jpg

(BTW, notice the huge bodies and small brains of dinosaurs!!!)

A big reason humans are the most intelligent species is that they have a much larger brain compared to their body size.  This brain size to body mass ratio is called the Encephalization Quotient “EQ” (a notion developed in 1973 by Harry J. Jerison PhD, Professor Emeritus, Psychiatry & Biobehavioral Sciences, UCLA).  Although EQ has some flaws, as shown in the chart below, it does a pretty good job of linking increased intelligence (in all species) with higher EQ values. 

CE_Ratio.jpg
(Once again, notice the really low CE values for the dinosaurs!) 

But, why should a ratio of brain to body size have anything to do with intelligence? The answer has to do with what the brain is asked to do.  Essentially, large animals with lots of body to control need a large portion of the brain dedicated just to controlling the body!  So, it isn’t surprising that sperm whales and elephants that are much larger than humans have brains with a large portion of their brains dedicated just to controlling their bodies. 

The same is true for the Neanderthal.  In a study by Oxford researchers led by Eiluned Pearce titled New insights into differences in brain organization between Neanderthals and anatomically modern humans published in the Proceedings of the Royal Society Biological Sciences in 2013, the researchers determined that in addition to having larger bodies than modern humans, Neanderthal also had bigger visual systems.  Relatively more of the Neanderthal brain was dedicated to controlling their bigger bodies and controlling and processing their vision!  As a result, there was relatively little brain left for the important higher cognition tasks and social development.  In other words, there wasn’t much brain left to face their daily challenges compared to modern humans!

This probably also explains why the Rhesus monkey and mole, both with larger CE ratios than humans, aren’t more intelligent than humans.   First, both have smaller brains than humans.  (Duh! with respect especially to the mole!!)  But, perhaps other functions of their brain are taking up valuable brain mass.  For example, a large portion of the mole’s brain is likely going to that area of bare pink skin on its snout that is covered in tiny tentacles that detect movement and the scent of prey and other moles, in stereo no less!!!

So, to answer the question of Does Size REALLY Matter?  The answer is YES! so long as your body is relatively small compared to your brain AND your brain isn’t being tasked with controlling dedicated systems like body control, vision or sophisticated smell!!

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Topics: Neurophysiology

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