How Relevant Is Brain Size To Human Intelligence?

The Jury Still Out On Brain Size

The term Brain size, may suggest that it has a bearing and influence on the intelligence of a given species. That is, the larger the Brain Mass, the more intelligent the organism.

The jury is still very much out on the relationship between Brain volume and intelligence

The jury remains out on the relationship between Brain volume and Intelligence.

There are many other factors to take into account such as body mass, and the way the Brain is structured. 

However, as we shall come to see, an influence which is possibly the most potent constituent in the Universe, is the elementary driving force underpinning Intelligence.

This influence is not readily recognized as such, even by Science.


To gain a clearer appreciation, of the relevance of Brain size to Human intelligence, we need to indulge in a little Greek.

We begin with the Cephalon, which is your head, complemented by your Encephalon which is the contents of your head. Known more commonly as your Brain.

Your Brain is the Cephalization, or Terminal, of your Nervous System.

What Is Cephalization?

Cephalization is the Evolutionary Driven concentration of Sensory Organs in the one region of the body of a creature. Usually, but not always, this region is the head. Your Cephalon.

The greater the Cephalization the easier that creature can Function in it's environment. And the more functions it can perform.

What Is Encephalization?

The term Encephalization, an expression that to date has not yet found it's way into many dictionaries, is used to denote a simple relationship between the body mass and Brain Mass of a given organism. 

Humans are one part brain and forty parts body so are mice

This simple relationship results in a ratio that allows comparison of Brain size between two organisms.

We Humans score high on this ratio. So too, do Mice and Birds.

Humans are one part Brain and forty parts body. So are Mice. Smaller Birds are one part Brain to twelve parts Body, and Elephants are one part Brian to to five hundred and sixty parts Body.

Notwithstanding the conspicuous difference between Bird and Elephant both creatures exhibit noteworthy Intelligence.

What Is Encephalization Quotient?

A more complex calculation and comparison used by science to gauge potential Intelligence is referred to as the Encephalization Quotient.

Encephalization Quotient, can be defined as, the quantity of Brain Mass, in excess of that determined to be required for an organism's body to function optimally.

This excess Brain Mass then, is available for higher Cognitive functioning.

To calculate this complex comparison requires the introduction of Allometry in the form of an equation. Which I won't mention.

What Is Allometry?

In a nutshell, Allometry, as applied to biology, is that field of scientific research that studies the relative growth of one part, or organ, of a creature, in comparison to the growth of the complete creature. And how that relates to the creatures Anatomy, Geometry, Physiology and Behavior.

Allometry makes many useful contributions to science

These parameters were incorporated into the previously non-mentioned equation by German born Biologist, Otto Snell, in the early 1890s. Employing empirically derived inputs. It is still used today.

Applying allometry to Biology furnishes useful contributions to scientific investigation by way of comparison. And it provides a handy platform for calculating the energy efficiency of any given Nervous System.

Nevertheless, due to the ever variable nature of the empirical inputs available, it can only be approximate in predicting how much Brain Mass is available for higher Cognitive functions. Though it does give a relative indication of possible redundant Brain Mass between species.

Potential Intelligence

Encephalization was a necessary and useful initial measure in comparing Brains across the board. It suggests that excess Brain Mass is available for enhanced intelligence.

Evidence is slowly gathering, however, that it will eventuate, that the jury will find in favor of the following factors as being the true assessment of Potential Intelligence:

  • Location, type, and density of Neurons within the Brain.
  • And perhaps elsewhere in the body. Such as the Heart and other Organs.
  • The role a particular Neuron's attendant support cells (Glia) play.
  • Synapse Action Potential activity.
  • Neural Networks.
  • Data transmission speeds between Neurons.

And - - -

  • Data transmission speeds between Neural Networks.

Development and utilization of that Potential Intelligence is another matter altogether. This is where you and I enter the picture, and exert influence on our own Intelligence. Via the Tools of Personal Development.

Something Additional Is Required

From a common-sense, logical point of view, it could be concluded that a larger Brain size offers the potential for greater Cognitive ability, but it is only one component.

The development and application of that potential intelligence is another matter altogether

Other elements, such as those mentioned above, are also required to be present to establish this Thinking capacity.

And as well as having these constituents in place, it would appear that something more is required to implement this superfluous to mere survival Cognitive Power.

This something extra is freely available to each and every one of us. And can be readily found in the mind expanding realms of wise Personal Development.

There is still much to be considered and settled in this Brain size and Intelligence discussion. So while the jury is deliberating, let's take a look at Brain structure.

Human Intelligence Rocks!

Next - Brain Structure And Personal Development

Return to Brain Size

Return To