IQ & Nature vs Nurture

Scientists have long been debating the relative contributions of genes vs environment, nature vs nurture, to our IQ level.

The following non-genetic / environmental factors have been shown to substantially impact intelligence levels.

Breast Feeding & IQ

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

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.

The Flynn Effect: Globalization & our knowledge industry

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.

The Flynn Effect in 5 nations

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. (This training exercise can be found here - I sell it!)

Summary

This data all suggests that the environment plays a strong role in determining our IQ – both in development, and in targeting brain plasticity in adulthood. A stronger role than I had once thought.