One of the oldest debates in the world is nature versus nurture.
It asks the question of whether we are more shaped by our upbringing and environment or by our genetics and innate traits.
This is especially important when it comes to intelligence.
Are you born smart or do you become smart? Or is it an even mix of both?
Let’s find out the truth.
Weighing genetics versus environment
Strictly speaking, genetics is what you’re born with, and environment is the situation and context you’re born and raised in.
How you show up in this world is genetics.
These are the tools you’re given to work with by your ancestors and their DNA that’s passed on to you.
How you are treated, educated and raised in this world is environment, including epigenetics, or traits which express themselves as a result of a certain environment.
These are the tools you’re taught to use and learn to develop.
The classic experiments for testing whether genetics or upbringing has more effect on your intelligence later in life have been done using identical twins raised in very different environments.
The findings generally showed a higher weight for genetics, but also demonstrate that many genetics don’t express themselves unless the environment allows and calls for them.
Most intelligence is inherited, but it’s not that simple…
Strictly scientifically speaking, there’s no doubt that most intelligence is inherited.
As the European College of Neuropsychopharmacology notes:
“Recent findings have shown that variation in total gray and white matter volume of the adult human brain is primarily (70-90%) genetically determined.”
However, the importance of upbringing, education and social factors in shaping intelligence are also a provably important and influential factor in determining an individual’s perspicacity later in life.
Let’s be real:
You may have more brain capacity than someone else simply due to your genetics.
Simply put, you may have won the genetic lottery in terms of intelligence due to your DNA.
But whether or not that brain capacity will be developed and used can depend quite significantly on environmental stimulation and encouragement.
Understanding phenotypes and gene expression
One of the key concepts in understanding how the environment affects gene expression is to grasp how our phenotype develops and refines itself.
Our phenotype is our body and our behavior coming together into a genetic whole. It includes personality traits and aspects of intelligence and intellectual ability.
The phenotype comes from genes and is an expression of genetic heritage, but it doesn’t just play out like a script.
It varies according to the situation.
“A gene is less like a computer program that is always obeyed to the letter, and more like a recipe that can be adjusted depending on the ingredients at hand…
“…When talking about the genetic contribution of intelligence, it’s important to remember that there is nothing deterministic or mechanical about how DNA emerges as complex and adaptive behavior in the real world.”
In other words, you may be born more or less smart than someone else.
But whether you will end up that way in 10 or 20 years definitely has a lot to do with the environment.
How much? Let’s investigate, starting right at the beginning…
The importance of early infant experiences
Our first experiences as new beings on this planet comes from where we are raised and fed, either with a mother or a guardian.
This has a massive impact on how our genes develop, as various studies now show.
When mothers give more care and love to their young, it makes them smarter.
A 2012 study led by child psychiatrists from the Washington University School of Medicine in St. Louis proved this.
“School-age children whose mothers nurtured them early in life have brains with a larger hippocampus, a key structure important to learning, memory and response to stress,” explains Jim Dryden.
The research out of Washington University has since been backed up by additional research including that done by Professor Regina Sullivan of New York University.
Sullivan’s study found that as mammals develop in very early life prior to 20 days old, the more they are cared for and loved the smarter and more awake they were later in life.
Those rats whose mother was away longer or more unpredictably, however, became distressed and tended to have shorter attention spans and lower intelligence later on.
The considerable importance of environment
Many environmental elements can significantly impair or enhance the intelligence of an individual. Debates vary over exactly how much, but it’s clear for the most part that there is real impact.
While identical twins do tend to show similar intelligence levels in some studies where they are raised in different environments, other studies report findings to the contrary, with those raised in better and more educated environments being more intelligent.
For example, a study with identical twins such as this 2003 study from the Virginia University, find that those raised in wealthier and more educated backgrounds tend to be smarter.
Study author Professor Eric Turkheimer noted that “homes led by better-educated parents produce real gains in the cognitive abilities of the children they raise.”
Of course, our environment isn’t just about having smart parents, nice toys to play with and a good education.
It also includes:
- The quality and nutritional value of the food we eat growing up
- The air quality, amount of exercise and health of the lifestyle we enjoy growing up
- The depth and closeness of our relationships and friendships growing up
- The social, spiritual, ethical, religious and cultural values instilled in us by parents, educators, coaches and authority figures
With so many factors in our environment that shape who we are, even the same two genetic codes from identical twins will undoubtedly express themselves in various ways, even if measurable IQ ends up being similar in some studies.
What’s been consistently demonstrated is that many aspects of our ability to be intelligent and potential are genetically determined.
But many aspects of whether or not that actually happens occur in our environment and in how our unique character interacts with and helps shape and use our environment.
Who we are in every way plays a large role in how we may respond to social or economic challenges in our environment, for example, which is why even some raised in very uneducated or difficult environments go on to accomplish great things.
It wasn’t only that they were genetically predisposed to intelligence, but that sometimes a difficult environment stimulates certain genes and phenotype traits to express themselves in contrast to the resistance of that environment.
In other words, every case is different.
Getting a clear answer
Getting a clear answer on whether intelligence is more determined by genetics or environment can be difficult.
Many people come down strongly on one side or the other, or state that it’s just an even split.
The consensus scientific view is that genetics have more importance, but due to gene expression and phenotypes, the environmental factor is also certainly important.
Brain volume and cognitive sharpness are largely inherited, however a multitude of studies show that those in higher socioceonomic households have higher intelligence.
The subject of gene-environment correlation is especially important here and tackles the subject of how our genes cause us to relate and interact with our environment.
For example, a child who is more shy may turn down attending academic clubs at school and hence develop less intelligence that he or she may have honed while being part of, say, the debate club or chess club.
Alternately, a more outgoing and sociable child may go to many academic clubs and camps and hence develop more of their intelligence despite having less inherited intellectual ability.
This points to why this debate continues to mystify and engage so many people.
For one thing it’s hard to separate the two factors, and for another, it’s clear that genetics and environment directly interrelate and overlap in many cases.
Christopher Bergland presents a thoughtful conclusion about this, noting that:
“Trying to measure “nature vs. nurture” scientifically is messy. It’s impossible to know precisely where the influence of genes and environment begin or end.”
What’s the consensus?
The consensus on a subject doesn’t necessarily mean it’s true, but it is useful to look at in order to get a picture of what the majority of experts currently believe.
In the fields of genetics, sociology and psychology, the consensus view is that intelligence is a mixture of genetic predisposition and environmental factors.
Each individual’s life is different, and each individual’s interrelation of genetics and environment is different.
Nonetheless, the current leading edge of research places a premium of genetics, which are generally weighted somewhat more important than environment, as I’ve discussed.
Nonetheless, no credible research would discount or rule out the influence factor of the environment and context in intelligence development.
The majority of experts conclude that while the precise admixture may be debated (50/50, 60/40, 70/30) it is undeniable that both elements play a decisive role in shaping how intelligent someone becomes later in life.