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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Additional Information

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 abilities 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 this concept. 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 intelligence.

Intelligence researchers have provided varying definitions. One of the earliest definitions was made in 1905 by Alfred Binet. He 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, 1n 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 genetic and environmental influences play a role in intelligence development.

There is no single intelligence gene. Instead, genetic influence is 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 with intelligence. Taken together, these 22 genes accounted for about 5% of the differences in IQ scores. A person’s intelligence is closely linked to the brain. Since 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 IQ’s 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 amount that genes that affect IQ appear to increase with age. This increase may be due to the fact that adults tend to select and shape their environment according to their genotype, so genetic differences are amplified. It may also be due to the fact that 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 linked 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.

Types of Intelligence (Part 3 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’s subjectively makes it nearly impossible to accurately measure intelligence, 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 or specific for educational levels. 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 is able to 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 essential elements:

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

It is believed that leaders who are able to relate to emotions and respond accordingly are more effective than traditional managers, the latter of which tend to 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 of intelligence, 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 4 of Is intelligence genetic?)

Intelligence correlates with a number of other variables. For example, people with higher intelligence scores are often more successful in school than less intelligent people and occupy higher occupational positions on average. People who are considered to have above-average IQ 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 intelligence appear to be more at risk, while average people suffer far less frequently.

Brain physiology (Part 5 of Is intelligence genetic?)

Neural studies conducted post-humaneously and through imaging techniques such as MRI suggest that intelligence 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. All of these factors correlate positively with intelligence (i.e. individuals with a larger overall brain volume have higher intelligence).

Other factors (Part 6 of Is intelligence genetic?)

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

Various other environmental factors like education, premature birth, nutrition, pollution, drug and alcohol abuse, mental illnesses, and diseases can have an influence on intelligence. Biological risk factors such as parental drug use, poverty, or poor mental health of the parent, can have 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 amount of free time to develop potential, parental education attainment, value on 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 large 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. Some think that the omega-3 fatty acids in breast milk contribute to that effect. However, there tends 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 intelligence from breastfeeding while others do not. However, other confounding factors, such as mother intelligence and socioeconomic status, were also present in these results. 

Artificial intelligence (Part 7 of Is intelligence genetic?)

Artificial intelligence (AI) is a concept associated with computer science and design. It refers to the replication of human intelligence within computing bodies and is increasingly used in many areas of society. Areas of application include GPS, speech recognition, search engines, 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 . 

A technology which exceeded this limit and that possibly shows reactions, which could be interpreted as emotional, would raise various ethical questions concerning 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!