Genetics and environmental factors play a role in determining a person’s intelligence level. But this topic has been one of the most debatable subjects throughout the history of psychology, and it is still controversial even today.
There are many disagreements about the fundamental nature of intelligence. Still, at the same time, psychologists and scientists put a lot of time and effort into studying the different genetic and environmental factors which can influence a person’s IQ level. This research has led to one important question: Which is more critical, genetics or environment?
An individual IQ level depends on many factors. First, genetics and environment can influence a person’s intelligence level, but some studies have proved that genetics have a more vital role in individual IQ levels.
On the other hand, many environmental factors can increase or decrease a person’s IQ level during their lifetime. These factors include education, nutrition, drug and alcohol, pollution, mental illness, diseases, or premature birth. These factors can also boost or reduce the role of genetics on intelligence.
As a result, today, psychologists believe that genetics and environment have an essential role in intelligence.
But, we want to know how much each genetic and environmental factor can affect IQ level. The thing about genetics, which can affect intelligence, is that there is not one single “intelligence gene” which can affect a person’s IQ level. But, multiple genes have a complicated connection, which can affect an individual’s intelligence.
For instance, if a person’s parents are tall, there is a high possibility which that person will also be tall. On the other hand, a person’s exact height can also be affected by environmental factors such as disease or nutrition.
Or another example is that a child might be born a genius, but if that child grows up in a low-income family or environment where he doesn’t have access to good food, nutrition, or educational opportunities, he won’t be able to score high on an IQ test.
In this blog, we discuss different genetics and environmental factors that can influence an individual’s IQ level and determine which one is more important and how it can affect a person’s life and experiences.
Is intelligence genetic or environmental
As we discussed, psychologists believe genetics and environment are vital to an individual’s intelligence level. But now, the main question is how much each genetic and environmental factor can affect a person’s intelligence level.
Based on many studies that have been done on twins, about 40 to 80 percent of the variations in intelligence are related to genetics, which indicates that genetics play a higher essential role compared to environmental factors in establishing a person’s IQ level.
Moreover, genetics and environmental factors will collaborate to determine how the inherited genes will manifest exactly. For example, as we mentioned, a child might be born with a high intelligence level, but a poor environment and bad living conditions can diminish their IQ level significantly.
Many studies suggested that the IQ scores of identical twins can be much more similar to fraternal twins. In addition, brothers or sisters raised in the same household have more like IQs compared to adopted children raised in the same environment.
Other biological factors can affect intelligence levels. These factors include maternal age, pregnant mothers’ exposure to dangerous drugs, and inadequate nutrition.
Many studies suggest that there is a high possibility that people with lower IQ levels have more bad experiences, such as victimization and harassment, which can lead to many consequences, such as emotional trauma, physical injury, or loss of property.
Some other examples are that identical twins raised in separate households don’t have many similar IQs compared to identical twins raised together in the same house.
Or children who drank their mother’s milk for 12 months or more usually have higher IQs at 30.
Other research suggests that firstborn children usually have higher IQs than their siblings.
The reason is that firstborn children will receive more attention from their parents and family. These studies also suggest that parents usually have more expectations from older children to perform better, while later-born children usually face fewer expectations from parents.
How do genetics affect IQ
When a person with a high IQ marries someone with a lower IQ, their kids may have any IQ level. If two parents with high IQs marry each other, their child may also have a high IQ, but there is also the possibility that their child has any IQ level, which is the same for two parents with low IQ levels.
The possibility of IQ level range is comprehensive and even surprising because many genes are engaged with IQ. But we should remember that environment plays a significant role as well.
There is no doubt that IQ is a product of both genes and environment. These factors can determine why a child’s IQ level differs from their parents.
The is a lot that environmental factors can do to influence a child’s intelligence level. For example, if a mother doesn’t eat properly or drinks alcohol too much when carrying a child, the baby’s brain can be damaged and won’t grow to its full potential. Conversely, children raised in a refreshing home environment have higher levels of IQ.
On the other hand, genetics can also determine the comprehensive range of IQ level possibilities because many genes are included in brain development. For instance, a child may inherit all the high IQ level intelligence genes from each parent and leave the lower IQ genes behind.
As a result, a child might be more intelligent than his parents, and of course, the opposite situation is also possible, in which a child might have a lower IQ than his parents.
When a characteristic is inherited from parents to children like this, it is called polygenic (multiple genes). Another characteristic example besides IQ is the height which can be passed on from parents to children.
Genes play a significant role
As we pointed out, IQ is polygenic, which means multiple genes interact to provide you with your IQ.
Many studies have been done in this field, mostly about twins with the same DNA, while fraternal twins’ DNA similarity is similar to any two brothers or sisters. Therefore, you can learn a lot by just comparing twins with each other.
Based on scientists’ research and the below results, the more the measured IQs are similar when a number is closer to 1.0. So if you and your twin have a score of 1.0, you have identical IQs. A 0.0 number means you have as different an IQ as possible. Some examples as below:
The same person (tested twice) 0.95
Identical twins—Reared together 0.86
Fraternal twins—Reared together 0.55
Heritability of Intelligence
Heritability is an estimation that determines how many traits in a population are related to genes. The estimation of intelligence’s heritability can be different based on the methods used for it. However, many researchers suggest that intelligence’s heritability is something between 60 percent to 80 percent.
Examples of hereditary Influence
Some examples of hereditary influences on intelligence come from the below studies:
- Studies on families show that intelligence runs in families.
- Twin studies show a higher link between identical twins in IQ than fraternal twins. This result stays the same even when identical twins who lived apart are compared to fraternal twins who lived together.
- Adopted children reasonably simulate their biological parents in intelligence level.
- Studies on families, twins, and adopted children have their complications and problems, and many controversial debates exist.
Environmental Factors that Affect IQ
Nutrition
Inadequate nutrition can affect a person’s intelligence level, mainly in the first few years of a child’s life. For example, many studies suggested that bad nutrition between the age of one and five can decrease an individual’s IQ level to 15 points.
Pollution
This factor can influence children’s IQ levels and lead to dementia when they age. In addition, many studies suggested that being exposed to polluted air in children is related to impaired performance at school and lower performance on IQ tests, which can affect their problem-solving and reasoning abilities.
Lead exposure
Lead is a toxic metal that can be found on the earth. Lead can also decrease children’s brain development if exposed to this toxic metal. As a result, children’s IQ will be reduced, and their behavior might change. For example, they might not be able to concentrate, their performance level may decrease at school, and they may be socially distant from everyone.
Stress
Trauma and stress can also influence a person’s IQ level, but this effect can vary depending on the trauma’s intensity. High-stress levels can decrease brain functions and even increase the risk of Alzheimer’s disease in older ages.
Education
Many studies suggest that education and IQ level are linked to each other closely. For example, a person’s intelligence level can increase between 1 to 5 points for every year of education.
Socioeconomic status
This factor includes the access of a family to different economic sources such as money, income, and also their status in society lack of access to financial sources, or in other words, poverty won’t let children use their highest level of intelligence.
Home has an essential role in a child’s first development years. Home situations can affect an individual’s behavior and point of view. The parent’s financial condition, environmental factors, neighborhood, and socioeconomic status, can also influence a child’s intelligence level.
Cultural and ethnic differences
Many studies suggest an inconsistency in average IQ scores between white people and other minority groups in countries like the USA. For example, black, Hispanic, and Native American people got lower scores on IQ tests on average than white people. However, this is still a controversial debate whether genetic or environmental factors are causing this difference.
Health and Physical Development
Physical and mental health is one of the most important factors for individuals to achieve what they want. Individuals with a physical or psychological condition might not have enough energy to achieve their goals as they should proceed. Some physical conditions, such as a lack of brain maturation, or disabled people may not be able to demonstrate a high intelligence level. Different diseases can also affect IQ levels.
Cognitive Mindset
This factor involves a set of experiences children will gain in their home environment. Some of the examples of the cognitive effects on the level of children’s IQ are as below:
- Providing motivating feedback to children and encouraging them can increase their IQ level as they grow older.
- Children who always receive negative feedback or get blamed by their parents will have lower IQ levels as they grow older.
- The relationship between mothers and children can increase or decrease the child’s IQ level. Engaged and enthusiastic mothers usually have children with high IQ levels.
To Sum it up
A big part of every individual’s intelligence level is related to genetics; a newborn child may be born with genius genes and a high level of intelligence.
Many studies suggested that 30-75% of Iq level variations can be related to genes, and different genes can affect an individual’s intelligence level. On the other hand, environmental factors can also significantly affect how much a person can benefit from their genetic potential during their lifetime.
For example, a child might have a high level of intelligence at birth. Still, environmental factors such as inadequate nutrition, Lacklack of access to good education, or poor socioeconomic status can influence that child’s intelligence level.
As a result, we can’t provide a solid definition for intelligence, but many psychologists and researchers define it as an individual’s cognitive abilities.
Eventually, a person’s intelligence can be affected by multiple factors and elements. For example, Genetics and environment work together in developing an individual’s IQ level. As we already know, genetics plays a vital role in a person’s or child’s cognitive development, but environmental factors can also impact intelligence.
All the genetic or environmental factors can increase or decrease a person’s intelligence level during their lifetime.
