Intelligence: Nature or Nurture?

In determining intelligence, what role do genetics and the environment play? To this day, this is one of the most controversial topics to debate in the history of psychology. It is often debated whether intelligence is significantly influenced by a person's environment or genes.

Psychology has spent a great deal of effort and time debating the various influences on individual intelligence, as well as disagreements about its basic nature. One of the major questions in psychology is: which comes first, nature or nurture?

Genetics and environment both influence intelligence, according to psychologists today. Let us now study how much influence each factor has.

Nurture

Children born into wealthier and more educated families are smarter than those raised in poorer homes. Researchers made this conclusion after studying biological brothers from different families and who had different IQs.  
Educated parents do things to make their children smarter, and this is not due to genetics.

Parents who are educated are more likely to speak to their children at the dinner table, take them to museums, and read to them at night, which have been shown to boost their children's IQs.

The IQ of first-born children tends to be higher than that of their siblings born later. The reason for this is believed to be the fact that parents give more attention to their firstborn children. Also, research suggests that parents expect older children to perform better on a variety of tasks, while later-born siblings have to face less task-focused expectations.

In most Western countries, more couples are looking to adopt than children up for adoption, so adoption agencies can select the best candidates and environments for adoption. The adoptive parents in the study were richer and more educated than the biological parents.

Nature

Reviews have found that heredity is one of the most influential factors determining a person's intelligence. It has been found that intelligence runs in families. To determine the effects of genetics on intelligence, researchers have identified processing speed, verbal comprehension, working memory, and perceptual organization as the primary cognitive domains.

Children born to parents with high IQs are likely to display high IQs as well. Parents pass on genes associated with intelligence to their children. Allelic studies confirm that children inherit genes from their parents. 

The influence of prenatal exposure to harmful substances, maternal age, and prenatal malnutrition may affect intelligence in addition to inherited characteristics.

There is evidence that people with lower intelligence are more likely to report crime victimization, which can have serious consequences including physical injury, loss of property, and psychological and emotional trauma. Furthermore, children have similar brain structures to their parents. 

Additionally, genes associated with cognitive abilities are heritable. Heredity, therefore, plays a significant role in determining intelligence. Children inherit genetic characteristics from their parents through sexual reproduction, which fuses the gametes of their parents through a biological mechanism well understood by scientists.

As a result, the genes linked to intelligence are inherited by children from their parents in the same way as the other genes, and they are expressed at the same level as genes that influence traits such as height, pigmentation, and gender.

Twin Study

Comparing the IQ scores of genetically related individuals with different degrees of genetic affinity has been one way to investigate this issue.

As identical twins, they share the same genes since they developed from a single fertilized egg that split into two. Identical twins have nearly 100% of their genes in common. It is more likely that their differences are the result of their environments than of hereditary factors.

Fraternal twins are like any other pair of siblings (brothers and sisters) because they are formed by two different fertilized eggs. 50% of their genes are in common.

In this way, IQ scores demonstrate both hereditary and environmental effects. Identical twins raised together have very similar IQ scores to fraternal twins raised together who have less similar IQ scores. 

Identical twins raised in separate homes have less similar IQs, indicating how their environments affect their development. Fraternal twins are less likely than identical twins to have identical IQ scores, but they are more likely than non-twin siblings to show IQ similarities. 

Remember that fraternal twins and non-twin siblings share the same degree of genetic relatedness. However, because fraternal twins are of the same age, their experiences in the environment are likely to be more comparable than those of their siblings who are of different ages. 

Both genetics and environment are involved.

Adoption and Foster Cases

Researchers concluded that if environmental factors contribute to the development of intelligence, providing more opportunities within the environment would increase IQ scores. 

The environment can perhaps increase IQ scores. A research study examined the IQs of African American children adopted from impoverished environments who were adopted into middle-class families. Each of the adopted families offered the adopted children many opportunities for socialization and education.

Researchers found that adopted children possessed IQs as high as 10 points higher than African American children raised in disadvantaged homes.

Researchers reported in a follow-up study that adopted children who are now adolescents had a high IQ score than African American children raised in their communities.

To Sum Up

Genetics and environment both play a role in how inherited genes are expressed. When a person has tall parents, they are more likely to be tall themselves. It is possible, however, for nutrition and disease to affect the exact height a person reaches.

It may be possible for a child to be born with genes for brilliance, but if they have a deprived environment to grow where he is malnourished and does not have access to education, he may not have a high IQ score.

This no doubt is one of the most controversial topics to debate. What do you think which factor has more influence on intelligence? 

Written By: Arushi Oberoi
Edited By: Harshdeep Kaur