According to Brazilian neuroscientist Suzana Herculano-Houzel the reason humans are so smart is not because humans have the biggest brains for our body size per se, (highest encephalization quotient) but rather because we have both a big brain and a primate brain. SHH’s theory is that primate brains are especially densely packed with neurons, so even though our brains are small compared to whales and elephants, the primate packing density gives us more cerebral neurons.
Well King Kong has a far bigger brain than humans do, and King Kong is also a primate, so by SHH’s logic, he should be smarter than people. And yet King Kong seemed no smarter than your average gorilla, which makes sense because King Kong’s huge body guarantees it would have a much smaller encephalization quotient than people do.
So while cerebral neuron count might be roughly as accurate as EQ when predicting the intelligence of real life species, it fails when it comes to fiction.
Well, then maybe we have the largest brain/body size ratio, scientists must have thought. Wrong again! that honor seems to go to small ants.
Well then maybe we have the largest brain/brain expected for our body size ratio? Bingo! What most distinguishes the human brain from that of all other animals is that it’s 7.6 times larger than statistically expected for a mammal of our size and probably well over 8 times larger than for an animal of our size.
No other creature comes close.
Our huge encephalization quotient allowed humans to conquer the World, accumulating more biomass than any other species except for cattle whose body-mass we’ve deliberately grown as our food supply.
Of course there’s far more to intelligence than just brain size adjusted for body size, but when comparing vastly different species who differ enormously on this metric, it seems to be a strong indicator.
Enter Brazilian neuroscientist Suzana Herculano-Houzel who commenter Race Realist has been blathering on about for years. While she agrees that humans are the smartest animal on the planet, she felt she had a more direct way of measuring it than brain size adjusted for body size. Indeed, she felt we could just ignore body size completely, and simply count the number of neurons in the cerebral cortex, and she came up with a very innovative way of doing so: using detergent to dissolve brains into a homogeneous soup of cell nuclei.
At first this method looked promising. By simply counting the number of cerebral neurons and ignoring body size completely, it seemed Herculano-Houzel had found a simple brain property that ranked humans in first place. In 2017 she wrote:
the human cortex, with an average 16 billion neurons…, has almost three times as many neurons as the twice-larger elephant cerebral cortex, with not even six. The second-largest primate brain, the gorilla, has about nine billion. Even the largest whales don’t have more than three or four billion. Most mammals have less than one billion.
Thus, the human brain has by far the most neurons in the cerebral cortex – that part of the brain responsible for personality, temperament, pattern finding, logic reasoning and planning for the future, making behaviour more than simply reacting to stimuli. That, I believe, is the simplest explanation for our remarkable cognitive abilities.
Herculano-Houzel’s star began to rise. Seeing a Brazilian woman make such a monumental scientific discovery was inspiring. She gave a TED talk and commenter Race Realist began drinking the kool-aid (or should I say brain soup).
However a 2014 study found ” the long-finned pilot whale neocortex has approximately 37.2 × 109 neurons, which is almost twice as many as humans”.
Thus despite Herculano-Houzel’s Herculean efforts, encephalization quotient remains the single best neurological proxy for intelligence at the inter-species level, or at least the only one that puts us humans where we belong: at the top.
On page 206 of Bias in Mental Testing, Arthur Jensen writes:
Not sure why Jensen considers all these correlations positive, unless zero is a positive number (I consider it neutral).
And I’m not sure why some commenters think weight lifting requires coordination when the correlation between strength (hand grip, chinning) and coordination (Pursuit rotor tacking, Mirror star tracing) is zero.
But maybe these are not the best measures of strength or coordination (mirror star tracing sounds more like a cognitive test than a physical one), but when I lift weights, I don’t feel like I’m using coordination. To me coordination is best measured by very fast paced tasks that require moving multiple body parts with exquisite timing.
Physical coordination probably correlates more with IQ than does any other physical ability. Daniel Seligman writes:
Contrary to certain stereotypes about athletes and intellectuals, physical coordination is positively correlated with IQ. Technical studies by the U.S. department of Labor report a 0.35 correlation between coordination and cognitive ability.
0.35 is very similar to the correlation between IQ and brain size; so there are at least two physical traits (brain size and coordination) that correlate moderately with IQ.
Some might argue that physical coordination is a part of intelligence since it’s largely a brain function. I define intelligence as the ability to use whatever physical traits one has as a tool to exploit whatever environment one’s in. I see coordination as one of those physical traits used as a tool by intelligence rather than part of intelligence itself, but it’s a meta-tool in that it controls the body which in turn controls the external environment.
The problem with including physical coordination in our definition of intelligence is that intelligence is only important because it’s what separates man from beast, and physical coordination fails to do that. Even if it were possible to put a man’s brain in a cheetah’s body, he would not be able to exploit the environment because his brain’s not evolved to control the cheetah’s body. But if a man’s brain could control what the cheetah did with its motor control, only then would the cheetah display the goal directed adaptive behavior we know as intelligence.
It’s like the Master Blaster character in Mad Max: Beyond Thunderdome. If Master’s brain was literally put in Blaster’s body, he might not have the coordination to win so many fights, but by telling Blaster how to use his coordination, he has given him his mind.
Feelings control intelligence
Intelligence is often defined as the mental ability to problem solve, but something is only a problem if it’s bothering us (i.e. cause us to feel pain or discomfort). Hence, feelings define the problems we use our intelligence to solve.
Intelligence controls physical coordination
Once our intelligence decides what behavior will solve a problem most efficiently, our physical coordination must direct our muscle movements accordingly. One could argue coordination itself is a mental ability and thus part of intelligence however by definition, abilities are only mental if they don’t cluster with sensory or motor functions, and physical coordination clusters with the latter. Even though coordination is part of the brain, it’s not fully part of the mind. It’s more neurological than mental per se.