Although the word “intelligence” has no single definition, it is universally associated with terms such as knowledge, mental capability, reasoning, judgment, imagination, cognitive function, and occasionally, adaptation. Over the years, the most common notion with regard to “intelligence” is that it simply is a desirable, advantageous attribute.
With numerous, continuing debates about intelligence, most of us wonder – where does intelligence really come from? Is intelligence genetic? Or is it a result of environmental and developmental influences?
The role of heredity
The fact that genetics does significantly affect or influence intelligence is beyond doubt, but how is it proven? There are two standpoints from which the determination of the heritability of intelligence is derived; a structural approach and a psychological approach
Studies on the heritability of intelligence started over a century ago. The relationship between genetics and intelligence has also been studied through brain structure. A very comprehensible approach in correlating general intelligence with the brain is through structural imaging of the brain’s white and grey matter volume.
It has been proven that brain structure measured using magnetic resonance imaging (MRI) correlates with scores from intelligence tests. The same correlation is seen with individual volumes of the brain lobes and cumulative volume of gray and white matter.
it is safe to conclude that brain structure does link genetic influence and intelligence in a quantitative and comprehensive approach. Furthermore, it has been proven that genetic factors are relevant to one’s distinct brain structure and in shaping one’s intelligence.
Another way of proving that intelligence really is genetic is through a psychological approach.
First of all, genetic expression greatly affects the innate physiology and development of the brain. Through a deeper understanding of the genes, we can further understand contributing fundamentals of evolution and behavior, including intelligence.
Second, individual differences in cognitive function and behavioral patterns are primarily caused by genetic differences. Therefore, understanding these differences through genetics can definitely provide the most succinct and logical explanations.
It has been shown repetitively through various approaches and methodologies, that genes do play a very crucial role on intelligence. Scientists have also learned that heritability does not only apply to intelligence, but more importantly, to every aspect of behavior as well.
However, much of the speculations regarding intelligence and genes almost always include the factor of environmental influences. As Toga and Thompson (2005) has pointed out, “correlations between related individuals show that both nature and nurture influence intelligence.” This insight leads us to a better standpoint that genes alone cannot account solely for intelligence.
With the theory of multiple intelligence becoming more and more accepted in the modern world, plus the belief that intelligence is a survival strategy, the concept of “intelligence” has become more complex in itself. As a result, the interplay between genes and environment generate infinite possibilities and complexities.
So is intelligence nature or nurture?
What needs to be proven now is how nature (genetics) and nurture (environment) both influence or affect intelligence. Ever since the article, “Intelligence: Knowns and Unknowns” by Neisser et al was published in 1996, much has been understood with regard to the synergistic relationship between genes and environment. In the article, it was discussed and emphasized that genetic expression does involve an environment.
When phenotypic traits (perceivable attributes from one’s genetic make-up) develop, it is highly possible that an environmental input can modify them to some extent. On the contrary, environmental effects cannot manifest without the presence of a preexisting structure, such as a genetic structure, to act upon.
So, is intelligence nature or nurture?
The ultimate answer is – it is a combination of both.
PIERMATTIA GENTILE ©