Intelligence is defined as “the ability to acquire and apply knowledge” or “Capacity for learning, reasoning, understanding, and similar forms of mental activity.”

So why does intelligence vary so much from person to person?

There are just as many reasons as there are snowflakes in a blizzard. We will cover some of the more widely accepted and scientific reasons here:

  • Mental Capacity
  • Genetic Attributes
  • Environmental variables
  • Difference in cultures

The truth is intelligence does vary on a broad scale. We assign numbers and classes to intelligence such as IQ points or phrases like “normal” “subnormal” and “supernormal.” We know this is the case. However, we still don’t completely understand why.

Mental Capacity

It was once widely believed that brain size correlated to intelligence. While we no longer tend to think this (Albert Einstein had an average sized brain, Plato a smaller brain), it stands to reasons that some mental capacity must be involved.

Using MRI to study active brains, scientists have learned that the capacity for intelligence has something to do with the density of the folds in the forebrain lobes. While a larger brain does not mean higher intelligence by default, the grey matter density of the cerebral cortex just might

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Our cerebral cortex is folded to increase the surface area inside the skull. The tighter and denser the folding, more surface area is available for use. It is widely speculated that higher surface area directly correlates to a higher capacity to acquire and apply knowledge.

Psychologists Ian Deary and Lawrence Whalley stated in their survey: “’Brainy’ children are not cleverer solely by virtue of having more or less grey matter at any one age. Rather, intelligence is related to dynamic properties of cortical maturation.”

Genetic Attributes

No two people are exactly alike. Not even identical twins. The same is true of our brains.

Genetics plays a large role in our intelligence level. Mom and Dad pass on to their children half of their genetic code. What varies (and what makes us all different) is which parts make up those halves.

If parents have two children, those children will share the same genetic makeup; however, one child may gain more intellect from the mother while the other gains more from the father.  Thus, because of genetics and heritability, intelligence will vary from one person to the next, even if their genetic markers are similar.

Environmental Variables

The first 5 years of a child’s life are referred to as the formidable years. During this time the brain will grow to 95% of its total size. The brain will then gradually increase over the next 15 years to its full size.

During those first five years, studies have shown that environmental factors such as location, upbringing, the poverty level of the parents and educational stimuli all play a part in the overall intelligence of that child.

Children brought up in poverty to low-middle class families have a lower intelligence than their middle class to upper-class counterparts.

“Being poor,” Richard Nisbett writes in “Intelligence and How to Get It: Why Schools and Cultures Count,” published Feb. 2 by W.W. Norton & Company Inc., “is linked with many environmental factors of a biological and social nature that lower IQ and academic achievement. These factors include poor nutrition, inferior medical care, a low rate of breast-feeding and parenting styles that are much less warm and supportive than those of higher socioeconomic status parents.”

Difference in Cultures

Where you are raised is just as important for intelligence as is how you are raised. Different cultures have different histories, languages, customs, and educational systems. As a result, they must think and grow differently.

If you are brought up in a culture that doesn’t have access to books, for example, you will have a lower propensity for higher intelligence. Based on the definition in the beginning, small tribes may be able to survive for centuries without ever learning how to read, but their ability to apply and absorb knowledge will be lower.

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Likewise, growing up reading or listening to music every day will have a higher impact on the ability to have a higher intelligence.

Other cultural factors include access to other cultures, language barriers and formal educations. Without these, you are less likely to be of a higher intelligence than someone who had full access.

“People in Western cultures, he suggests, tend to view intelligence as a means for individuals to devise categories and to engage in rational debate, while people in Eastern cultures see it as a way for members of a community to recognize contradiction and complexity and to play their social roles successfully,” Nesbit said.

Potential and Beyond

We may never fully understand how or why we have a wide difference in intelligence. Each person is different. We are made from different pieces and raised in different worlds.

What we do know is that our brains can reach genius levels of intelligence. We do not know if it is possible to become genius over time or if we are simply stuck with what we are born with.

Children begin with a different intelligence level and during their adolescent years these levels will rise and fall. How much and in which direction is based on a myriad of factors. It also depends on the child.

If they don’t put in the effort to gain, apply and knowledge, they will lose it. Intelligence within the first 5 years of life is a basic “use it or lose it” scenario. Our brains produce grey matter folds and synapses fire at higher rates.

If the brain isn’t stimulated for growth, it will begin to shut down. Genetic factors play a significant role in how much we can absorb and how quickly we can raise our intelligence or how quickly it will diminish.

A healthy body and a healthy mind will help increase your intelligence. However, you are different. Just like everyone else.

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