Intelligence is not under genetic control: you can choose to change it
By Mark Ashton Smith, Nov 2009 – for The Self Improvement Blog
Irene’s note: Thank you, Mark, for this great article. all readers of the SI Blog to take a serious look at this article, particularly the section on nutrition. If you eat margarine, you will have a surprise. I encourage you to visit Mark’s website at http://www.iqlift.com/
Whether intelligence is largely determined by genetics or environment has long been hotly contested. Scientists have generally estimated that the genetic contribution lies somewhere between 50% – 80% – that most of our intelligence is under genetic control.
“Many if not most experts on intelligence in the late twentieth century believed that intelligence and academic talent are substantially under genetic control — that they are wired in and more or less unfold in any reasonably normal environment. Such experts were suspicious about the likely effect of any effort to improve intelligence and were not surprised when interventions such as early childhood education failed to have any lasting effect.” (Nisbett, Intelligence and How to Get It: Why Schools and Culture Count, 2009.)
Many scientists have doubted that people can become smarter as a result of improvements in education, changes in society or personal choices. And some educational administrators have now adopted this attitude in their pedagogy.
This article gives compelling reasons to challenge this attitude.
Identical twin studies and ‘heritability’
The standard statistic used to measure the contribution of genes to a trait like intelligence is heritability. Heritability is the proportion of variation in intelligence in a population that can be accounted for by genetic factors rather than environmental ones. If everyone took an IQ test) and scored exactly 100, we couldn’t get a heritability estimate. We need differences in scores. IQ scores are in fact spread out like a bell curve, with most people scoring around the average (100), and some people scoring low and some high. What accounts for this variation in scores? Why do some people score high and some low? Is it entirely due to genes? Is it entirely due to differences in upbringing or diet? Or is it a mix of both genes and environment? Heritability is the statistic that estimates the inherited genetic contribution to the mix of influences.
The correlation between IQ scores of identical twins who have been adopted and reared apart in different household and educational environments directly measures heritability. Identical twins raised separately following adoption show a high correlation (a measure of association) of 0.72 (out of a total of 1.0) for intelligence. In other words, if you know one twin’s intelligence, it strongly predicts what the other twin’s intelligence will be – despite their different rearing environments. It is this twin data that is the strongest evidence for a large genetic component to intelligence. Identical twins have identical genes.
Problems with identical twin studies and the ‘heritability’ statistic
For this identical twin methodology to be valid, it’s important that the twins are raised in entirely different environments. But there are many ways in which even adopted twins, separated at birth, share the same environment. First, identical twins share the same fetal environment which is known to influence intelligence. Prenatal environment has an influence on intelligence even for non-twin brothers or sisters that share the same womb consecutively. Second, twins are likely to be selectively placed into similar (but separate) adoptive homes – they are certainly not just ‘randomly’ assigned to different households which is what is needed for an accurate heritability measure. Third, adoptive families have strong similarities in the value that they place on child raising: they tend to share similar educational values. All these environmental factors contribute to that 0.72 correlation between separately adopted identical twins’ IQ scores, but they are not taken into account by the classic studies that come up with high heritability measures of between 0.50 and 0.80. Traditionally it has been argued that if identical twins are reared separately in different households after birth, if they are generally similar in their level of intelligence this HAS to be due to genetics, but here we can see that this similarity is due in part to all these other factors too. If you take these other influences into account it is clear that the heritability of intelligence has been exaggerated. The environment has a much greater impact than we have been led to believe. We can conclude that our environment (including parenting, diet, physical health and exercise, education, and targeted brain training) has a greater influence on intelligence than our genes do. This has been argued with painstaking scientific rigour by Nisbett in his 2009 book Intelligence and How to Get It: Why Schools and Culture Count.
What environmental factors change your intelligence?
Breast feeding
The duration of breastfeeding during infancy has been associated with higher IQ in children. Breastfeeding during infancy is associated with enhanced childhood cognitive development by 2–5 IQ points for full-term infants and 8 points for those of low birth weight. These are striking effects. If your baby is premature it is particularly important to breast feed – or supply the equivalent nutrients – for the child’s cognitive development.
Nutrition and intelligence
In a recent carefully controlled study looking at the association between intelligence and diet at 3.5 and 7 years, with a sample of 591 children, a number of dietary factors to be significantly and positively associated with intelligence. These included the following:
Breads and cereals
At 3.5 years the difference in total IQ scores for children who ate breads or cereals four or more times per day was 4 points higher than for children not consuming bread and cereals at these levels. Breads and breakfast cereals in this study were the main sources of iron and folate, both of which are known to be important in cognitive development.
Fish
Children who ate fish at least weekly at 7 years of age had significantly higher IQ scores than those children who did not, with a difference of about 3.5 IQ points. Fish contains a number of nutrients that have been associated with cognitive functioning. For example, fish is a good source of protein, bioavailable iron, zinc, vitamin B-12 and iodine. Seafood is also a good source of vitamin B-12, iron and zinc. Importantly, fish provides a rich source of omega-3 which is known to benefit cognitive development.
Margarine
Children who ate margarine daily had IQ scores that were approximately 3 points lower than children who did not. This negative impact of margarine on IQ was even greater for children who were born underweight. At 7 years of age, these children who ate margarine at least daily had a 6 point lower IQ compared to 7 year olds who did not eat margarine daily! Staying clear of margarine is particularly important for babies who are born small.
Butter, on the other hand, was found not to have a negative impact on intelligence. At 3.5 years of age butter was in fact positively associated with intelligence for babies born underweight. So don’t confuse margarine and butter in your baby’s diet! Stick to butter.
It is likely that it is the trans fatty acids or hydrogenated fats in margarine that are the culprit. Trans fatty acids have been associated with poorer cognitive performance in adults. Trans fatty acids may impair the metabolism of ‘smart fats’ like Omega 3.
Globalization & our ‘information processing age’
There has been a rise in the average IQ score of around 3 points per decade (although the figure varies from country to country) throughout the 20th century, from the time standardized intelligence tests were first used. A steady rise of intelligence has been observed consistently across the globe, not just western developed countries. Back in 1955 when the Wechsler Adult Intelligence Scale (WAIS) was first published, the average score for 20 year olds was 100 – the test was designed so that the average would be 100. But 20 year olds taking the same exact test now score an average of over 115! Intelligence levels have increased throughout the population. This is called the Flynn Effect, named after the psychologist who identified it and brought it to our attention.
These large increases in intelligence throughout the 20th century show conclusively that intelligence can be changed, on a national basis, by non-genetic influences. Better nutrition is likely to account for some of this IQ increase. In addition, the vast expansion of education – on a global scale – has had a great impact.
Many studies find that children who do not attend school score lower on the tests than their regularly attending peers. In the 1960s, when some Virginia counties closed their public schools to avoid racial integration, compensatory private schooling was available only for white children. During this period, the African-American children who received no formal education fell back at a rate of about six IQ points per year. Length of average schooling – throughout most countries globally – has steadily increased over the past century.
As Nisbett argues, the substantial impact of education on IQ gives out a positive message: If all kids are capable of learning under the right circumstances, parents and teachers should never give up on children who appear to be low performers. Everyone has the inherent ability to be smart.
Along with education, cultural changes, all of which make the world more intellectually challenging and stimulating in our global ‘knowledge economy, are likely to have had a great impact on increasing intelligence levels.
Adult brain training
Intelligence levels can be changed not just through childhood and the process of education and enculturation. Recently a brain training exercise for adults has been successfully developed by Dr Jaeggi and her colleagues at the University of Bern in Switzerland and the University of Michigan and the States, that has been demonstrated to improve fluid intelligence – our ability to reason and problem solve in new situations – by a striking 40% as measured by a well-known, standardized IQ test. This resulted from just half an hour of training per day for 19 days. Training with this exercise called the ‘dual n-back’ has also been shown to increase neural activity in part of the frontal lobe known to be involved in higher cognitive functioning, and to increase the density of neurons’ receptors for dopamine, a neurotransmitter involved in higher cognition. This is called synaptic plasticity – it occurs at the level of the connections between individual neurons.
Conclusion
We can conclude with a very positive message for those of us who like to take life into our own hands and make informed choices. Intelligence is not hard-wired for ourselves or our children. We can choose to improve our cognitive functioning and become smarter. In becoming smarter, we have more cognitive resources to help build the lives that we want for ourselves and our children.
