Intelligence (Sniekers, 2017) – Is intelligence genetic?

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Nebula Genomics DNA Report for Intelligence

Is intelligence genetic? We created a DNA report based on a study that attempted to answer this question. Below you can see a SAMPLE DNA report. To get your personalized DNA report, purchase our Whole Genome Sequencing!

Is intelligence genetic? Sample report from Nebula Genomics
Is intelligence genetic? Sample variants from Nebula Genomics
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This information has been updated to reflect recent scientific research as of May 2021.

What is intelligence? (Part 1 of Is intelligence genetic?)

Intelligence is a collective term in psychology for cognitive or mental ability. It refers primarily to the ability to use the totality of differently developed general cognitive ability to solve a logical, linguistic, mathematical, or meaning-oriented problem. More broadly, it is the ability to learn from experiences and adapt to changing environments.

General psychology, differential psychology, and neuropsychology are all fields concerned with the topic. Its study in the field of general psychology under the aspect of information processing is today often referred to as cognitive psychology. This, in turn, draws on methods and findings from brain research, developmental psychology, and, increasingly, artificial forms.

Intelligence researchers have provided varying definitions. One of the earliest definitions was made in 1905 by Alfred Binet, who described it as “Judgment, otherwise called ‘good sense,’ ‘practical sense,’ ‘initiative,’ the faculty of adapting one’s self to circumstances.” In 1944, David Wechsler described it as “The aggregate or global capacity of the individual to act purposefully, to think rationally, and to deal effectively with his environment.” This is one of the first times the concept was associated with rational thinking. 

Howard Gardner, in 1993, implicated problem solving as a necessary component. Later scientists also define intelligence as adaptability and the ability to change one’s cognitive functioning to adapt to new information. 

Is intelligence determined by genetics?

Both environmental and genetic influence play a role in cognitive development.

There is no single intelligence gene or single nucleotide polymorphism (SNP) associated with cognitive ability. Instead, it is a complex trait determined by a large number of specific genes and alleles, of which each one contributes a small amount to overall intelligence. Polygenic scores may help distinguish risks for individuals. A large meta-analysis conducted in 2017 identified 22 genetic variants most likely related to cognitive functioning. Taken together, these 22 genes accounted for about 5% of the differences in IQ scores. Since a person’s cognitive mind is closely linked to the brain, and at least half of the genome contributes to the brain’s makeup, researchers suspect there are many more genes related to both.

Genetic studies on twins have demonstrated that between 57% and 73% of general intelligence may be hereditary. This point is further made through studies demonstrating that identical twins have IQs that are more similar than those of fraternal twins. Meanwhile, family studies have shown that siblings raised in the same home have IQs that are more similar than those of adopted children raised together in the same environment.

Twin babies
Twins raised together tend to have similar IQs. Flickr.

The number of genes that affect cognitive ability appears to increase with age. This increase with age may be because adults tend more than children to select and shape their environment according to their genotype, so genetic differences are amplified. It may also be because childhood cognition is still developing, negating some of the genetic effects. 

In 2018, another study showed over 500 genes linked to intellectual ability. Some of these genes are also related to other biological processes, such as longer lifespan.

Certain forms of intellectual disability are genetic. These include Down syndrome, fragile X syndrome, and (if untreated) the consequences of phenylketonuria.

Current Research On Intelligence (Updated May 2021)

A recent study published in 2021 titled “Using DNA to predict intelligence” had three objectives. The first is to review how the DNA revolution has transformed the ability to predict individual differences. The second is to consider the impact of genome-wide polygenic scores (GPS) on intelligence research. The third objective is to consider the societal impact of the polygenic scores. 

The study concluded that the DNA revolution has significantly contributed to how individual intelligence can be predicted, although the confidence is still relatively low. It highlighted that “In 10 years, the ability to predict intelligence from DNA has gone from 0% to 10%.” The research further explained that the availability of genome-wide polygenic scores (GPS) before conception, prenatally, and at birth would significantly impact society. 

A landmark 2018 study published in Nature Reviews Genetics by Robert Plomin & Sophie von Stumm suggest that polygenic scores derived from GWAS of intelligence can now predict 4% of the variance in intelligence.

A review published in Molecular Psychiatry summarized and critiqued the last 10 years of DNA research on cognitive ability, including the discovery of genetic loci associated with intelligence, DNA-based heritability, and genetic correlations with other traits. Many of the studies cited in this article include sample sizes of over 200,000, indicating decent confidence in the results.

After reviewing several independently conducted research projects, the study reached the conclusion that genes may contribute significantly to intelligence. However, these results have not been backed up.

Types of Intelligence (Part 4 of Is intelligence genetic?)

Human Intelligence

This is a category that most people think of when they think about the main theories of intelligence. It is defined by the ability to perform high levels of cognitive reasoning. It enables humans to remember things and use those descriptions in future behaviors. It also allows individuals to form concepts and employ reason, including the capacities to recognize patterns, innovate, plan, solve problems, and communicate. 

Deductive versus inductive reasoning
Intelligence is the ability to solve problems or apply information. Wikipedia. CC-Attribution-Share Alike 4.0 International

Intelligence is different from learning. The latter refers to the act of retaining facts and information, while the former is about the ability to apply what is learned to new situations.

Intelligence Quotient (IQ) Test

Although it subjectively makes it nearly impossible to measure intelligence accurately, the most used measurement is the IQ test. This intelligence test assesses ability in general or within a specific range in comparison to a reference group. The baseline an individual is measured against is always in reference to their peers. 

The “population-representative” reference group can be age- or school class-specific (especially for children and adolescents) or specific for educational levels (for example, high school students or professional groups). In today’s tests, the distribution of test results from a sufficiently large sample is used to determine the norm value. According to a normal distribution, about 68% of the individuals in this reference group have an IQ in the so-called middle range between 85 and 115. Norms must be examined for stability over time and re-estimated when they become obsolete.

Emotional Intelligence (EI)

EI is becoming a common concept in professional careers and leadership training. It is contrasted with general intelligence, where the latter focuses on general cognition, and the former focuses on emotion. Someone who has EI can recognize, empathize, and manage their own emotions as well as the emotions of others. 

The American psychologist, Daniel Goleman, was essential in popularizing this concept. He defines five basic elements:

  1. Self-awareness
  2. Self-regulation
  3. Motivation
  4. Empathy
  5. Social skills

It is believed that leaders who can relate to emotions and respond accordingly are more effective than traditional managers who follow a script for working with employees. 

Social Intelligence

Social intelligence is the capacity to know oneself and to know others in social situations. It develops through continued experience with people and learning from success and failures in social settings. It also relies on the ability of an individual to pick up on social cues. While it is related to other forms, especially EI, it is most often considered a separate category, distinguished by its role in group or social settings. 

Other Forms

According to the multiple intelligences theory, the concept can be further broken down into specific life areas; many focused on different areas of the brain:

  • Musical 
  • Bodily-kinesthetic
  • Interpersonal
  • Verbal ability-linguistic
  • Logistical ability-mathematical
  • Naturalistic
  • Intrapersonal
  • Visual-spatial
Multiple intelligences
Intelligence can be broken down into multiple areas. Wikipedia. Creative Commons Attribution-Share Alike 4.0 International.

Correlation with other Variables (Part 5 of Is intelligence genetic?)

Cognitive ability correlates with several other variables. For example, people with higher scores are often more successful in school than less intelligent people and occupy higher occupational positions on average. People considered to have above-average intelligence also generally live healthier lives and have a longer life expectancy.

However, it may also correlate with certain diseases. For example, intelligent people are more likely to be nearsighted. There is also a correlation with certain hereditary diseases.

For mental disorders such as schizophrenia, people with both particularly high and low cognitive ability appear to be more at risk, while average people suffer far less frequently.

Brain physiology (Part 6 of Is intelligence genetic?)

Neural studies conducted post mortem and through imaging techniques such as MRI suggest that cognitive ability correlates with brain structure and network connectivity. Some of these correlations include overall brain volume, grey matter volume, white matter volume, white matter integrity, cortical thickness, and neural efficiency. These factors correlate positively with intelligence (i.e., individuals with a larger overall brain volume have higher intelligence).

Other factors (Part 7 of Is intelligence genetic?)

Development is also influenced by socioeconomic status, which tends to determine whether an individual will be given a chance to reach their intellectual potential. For instance, genetic research shows that when identical twins are reared apart, they tend to have less similar IQs than identical twins raised in the same environment.

Various other environmental factors like premature birth, education, pollution, nutrition, drug and alcohol abuse, mental illnesses, and diseases can influence cognitive ability. Biological risk factors such as parental drug use, poverty, or poor mental health of the parent, can have an especially significant negative impact on intelligence development. Two of the most talked-about factors related to these biological factors are socioeconomic status and nutrition. 

Socioeconomic environment

Children from disadvantaged families tend to score lower on IQ tests than those from privileged families, who tend to have high IQs. Much of this role could be an extension of parental influence. For example, parents from higher socioeconomic backgrounds tend to have a greater ability to expose their children to educational pursuits. Other factors such as the amount of free time to develop potential, parental education attainment, the value of education, nutrition, and overall health are also correlated to more privileged households. 

Nutrition

There is scientific evidence to suggest that malnutrition may impair cognitive abilities, especially when experienced in infancy and during early childhood. Scientists believe the lack of certain micronutrients, such as omega-3 fatty acids, vitamin B12, and folic acid, play a prominent role in lower IQs.

Fruits and vegetables
It’s widely believed that some combination of nutrients affects intellectual potential. Pixabay.

Prenatal and early nutrition are linked to brain structure, behavior, and intelligence. There is a positive correlation between children who are breastfed and heightened IQ scores, and it is thought that the omega-3 fatty acids in breast milk contribute to that effect. However, there tend to be conflicting results about whether this is true and to what extent. 

Some scientists believe there could be a genetic predisposition to which some babies experienced heightened cognitive ability from breastfeeding while others do not. However, other confounding genetic factors, such as mother intelligence, and socioeconomic status, were also present in these results. 

Artificial intelligence (Part 8 of Is intelligence genetic?)

Artificial intelligence (AI) is a concept associated with computer science and design. It refers to replicating human intelligence within computing bodies and is increasingly used in many areas of society. Areas of application include GPS, speech recognition, machine translation, search engines on the internet, face and fingerprint recognition technologies, robots, etc. AI is also used in computer games for computer-controlled opponents. 

AI often mimics the neural networks in the human brain. Machines are thus becoming capable of learning in a similar way. For many applications, they are being taught to analyze data, learn from human inputs, and apply the new knowledge to a different problem.

What AI lacks so far, however, is self-awareness, consciousness, and emotions. 

A system that shows intelligent behavior remains only a tool as long as there is no self-awareness and no motivation to act out of “own” drive and pursue “own” interests. 

A technology that exceeded this limit and that possibly shows reactions, which could be interpreted as emotional, would raise various ethical questions concerning the rights and responsibilities of such a system. Among other things, it would have to be discussed whether a “biological” intelligence should be valued fundamentally differently from a “technological” one.

If you liked this article, you should check out our other posts in the Nebula Research Library!