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Influences on Intelligence

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Influences on Intelligence

We all know someone who has a very high IQ - maybe a friend who can solve math problems quickly or someone who appeared to be a "walking encyclopedia". Maybe you've asked yourself, how did he get so good at this? Did he inherit his high intelligence from his parents? Did his environment shape his intelligence?Two questions need answers: Is there a gene for intelligence? And, is intelligence genetic or environmental?

Influences on Intelligence, A woman holding a book and pointing to the scribbles illustrating intelligence, pexels.com, StudySmarterA woman holding a book and pointing to the scribbles illustrating intelligence, pexels.com

  • We will dive into genetic influences on intelligence first.
  • Then, we will explain what the biological influences are on intelligence.
  • We'll look at how heredity influences intelligence.
  • Lastly, we will look at environmental factors that impact intelligence.

Genetic Influences on Intelligence

There is no one specific gene that will dictate a person's level of intelligence. Instead, it is a combination of different genes influencing different components of intelligence. The CHRM2 gene has been identified to stimulate brain connections involved in various cognitive activities and associations of the SNAP-25 gene in nerve cell communication. Specific sequences in the dysbindin-1 (DTNBP1) gene can produce minor differences in IQ.

In a meta-analysis including data from over 78,000 individuals, researchers found 40 genes, of which the FOXO3 gene and CSE1L gene had the strongest association with intelligence, with a role in apoptosis, or cell death (Sniekers et. al, 2017; as cited in Carson, 2017). This suggests that intelligence may also depend upon the preservation and normal functioning of the nervous system.

Is Intelligence Genetic or Environmental?

The answer is that both genetic and environmental influences can affect intelligence. As shown in twin and adoption studies, genes have a more significant impact on cognitive differences than environmental influences. IQ similarities are stronger among identical twins than in those less genetically related, such as adopted children and their adoptive parents.

Influences on Intelligence, Identical twins smiling at the camera, pexels.com, StudySmarterIdentical twins smiling at the camera, pexels.com

The evidence of environmental factors shows that children are not born with fixed levels of intelligence.

Twins raised in the same rearing environment have more comparable IQs than twins raised in different households. Fraternal twins raised similarly have more comparable IQs than non-twins who received different nurturing.

On the other hand, other psychologists feel that a child's formative environment shapes intelligence, such that exposure to different settings can affect the development of cognitive skills.

Biological Influences on Intelligence

Let's look at some biological factors that are non-genetic in nature.

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Brain Structure and Efficiency

The thickness of the outer layer in some brain regions (e.g., frontal and temporal lobes), and the volume and number of nerve cells have been linked to intelligence. The temporal lobes mainly focus on memory, verbal, and non-verbal learning, while frontal lobes are responsible for the mental skills needed in daily living, such as planning, organizing, and even behavioral and emotional responses in achieving one's goals.

Intelligence is also positively associated with brain activity, whereas people with higher IQs use less brain capacity to work on tasks efficiently.

Hereditary Influences on Intelligence

Twin studies demonstrate a genetic aspect in people's IQs. Identical twins show similarities in brain structure and function and intelligence in other areas such as music, sports, and language. Even their IQ test results are comparable to those who took the same test twice.

Among adopted children, similarities in intelligence with their adoptive families are apparent in childhood. As they grow older, these similarities wane as experiences accumulate, and they become more like their biological parents, exhibiting genetic influences on intelligence. The impact of genes on intelligence becomes stronger in adulthood.

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Cultural Influences on Intelligence

Language, customs, and early-life experiences affect the intelligence scores of children whose culture doesn't emphasize Western schooling, or those who aren't well-adapted to the types of questions seen in conventional intelligence tests. Certain cultures prepare children to adapt to the environment in which they live, where they are expected to farm or have certain occupations that don't need formal schooling.

Families' conversational styles can also affect how well a child does in intelligence tests.

Influence of Environment on Intelligence

Let's now look at how environment impacts intelligence.

Family Environmental Influences

As you may expect, the familial environment is seen as having a big impact on intelligence.

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Parents' Educational Background and Culture

The educational level of parents is associated with their children's IQ. Parents who've had more education are more likely to be motivated in their children's development. They can inspire their children to learn through their example and create a positive and intellectually stimulating home environment to help increase their children's IQ.

Parenting practices shaped by culture also affect IQ and test scores, such as in one experiment conducted by Segal and Hur (2008; as cited in "IQ: Greatly Influenced by Early Family Life," 2015).

Two identical Korean twins raised in different cultures had varied verbal IQ scores and performance IQ scores. As the researchers argued, the twin raised in the United States got a higher verbal IQ score, possibly due to greater emphasis on language and the foster mother being a speech pathologist.

The other twin raised in South Korea got a higher performance IQ score, possibly due to greater emphasis on math skills and concepts in school. This study demonstrates the likely effects of parents' culture on early development and IQ.

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Home Environment

Chaotic family environments (e.g., loud noises) and adverse events experienced in early life negatively affect children's intelligence. They have lower scores on IQ tests and struggle in cognitive development. Insufficient intellectual and emotional support also affects intelligence. Ensuring a positive home environment may help increase children's intelligence.

Socio-economic Status

Children with parents who have higher incomes tend to have higher IQs than those from low-income families. Poverty also lowers IQ; averages in IQ of children from lower socioeconomic groups are lower than middle-class children by about 10-15 points (Bearce, 2009). Problems with access to healthcare also add to the burden.

Parent-child Relationships

Intelligence increases when a child feels cared for, encouraged and loved in his early years. Family nurture displays a more significant impact on intelligence in children's early years; those with higher IQs experience more positive environmental influences. Here we can see the importance of parent-child relationships as parents are the child's first teachers; it is essential to create experiences that will positively impact their intelligence.

Intelligence also relates to a child's dependence upon his parents, where more dependence among preschool and elementary students may indicate lower IQ than those who feel independent. A sense of belonging and independence at home can affect a child's academic achievement and intelligence test scores.

Mother-child interactions, for instance, breastfeeding, can also increase intelligence due to the fatty acids present in the breastmilk and the mood and overall interaction between the mother to her child, which affects not only physical development but also IQ scores.

Daily verbal interactions and applying complex words when communicating with children also help increase their intelligence.

Other Environmental Influences

Let's consider some other environmental influences now.

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Education

A link exists between the length of schooling and children's intelligence. Baltes and Reinert (1969; as cited in Deary and Johnson, 2010) found that 8-year-old German children who got an extra year of schooling performed similarly to 10-year-old students who had the least amount of schooling. Overall, school attendance promotes intelligence because of cognitive abilities learned there, such as metacognition. Intelligence also declines among school dropouts for every school year missed.

Nutrition and Physical Activity

Nutrition also affects IQ, in that children who receive adequate nourishment have higher IQs than children who experience malnutrition. In addition, a pregnant mother's consumption of toxic substances can result in issues like fetal alcohol syndrome, which causes mental decline, language delays, and poor motor coordination. Children who engage in physical activities tend to have higher IQs, as seen in a study where the high IQ group did more than five hours of exercise per week (Makharia et al., 2016).

Place of Residence

Makharia et al. (2016) researched 1,065 Indian children between 12 to 16 years, finding that those who lived in cities and towns had higher IQs than those in the villages.

Importance of Environmental Influences on Intelligence

Environmental influences allow for opportunities to promote intellectual stimulation that will, in turn, help shape children to become healthy and productive adults in the future. What nature lacks, nurture can help fill in the gaps. Environmental influences strengthen or weaken intellectual growth.

Identification of environmental influences helps emphasize the positive early life and educational experiences and provides programs and interventions, especially for disadvantaged children from low-income families or with developmental delays.

Influences on Intelligence - Key takeaways

  • Genes and environmental influences are at play in intellectual growth.

  • Findings from twin and adoption studies show heritability of intelligence and evidence of gene interaction with the environment. Many similarities among twins exhibit hereditary influences such as brain function and activity during mental tasks.

  • Biological influences on intelligence include brain structure and volume.

  • Cultural influences can affect IQ scores among children because of the different customs, family expectations, and practices present in their place of residence.

  • Parents are children's first teachers. They influence intelligence significantly through their educational level, income, home environment, and parent-child relationships.


References

  1. Bearce, K.H. (2009). Chapter 8: Intelligence. https://www.mccc.edu/~jenningh/Courses/documents/Handout-Intelligence_000.pdf
  2. Carson, J. (2017). Genetics: Recipe for intelligence. Nature Human Behaviour, 1(7), 1-1.
  3. Deary, I. J., & Johnson, W. (2010, May 26). Intelligence and education: causal perceptions drive analytic processes and therefore conclusions. OUP Academic. https://academic.oup.com/ije/article/39/5/1362/802787
  4. Makharia, A., Nagarajan, A., Mishra, A., Peddisetty, S., Chahal, D., & Singh, Y. (2016). Effect of environmental factors on intelligence quotient of children. Industrial psychiatry journal, 25(2), 189.
  5. (2015) "IQ: Greatly Influenced by Early Family Life," Intuition: The BYU Undergraduate Journal of Psychology: Vol. 11: Iss. 1 , Article 4.

Frequently Asked Questions about Influences on Intelligence

Both genetic and environmental influences can affect intelligence. 

There is no one specific gene that will dictate a person's level of intelligence. Instead, it is a combination of different genes influencing components of intelligence. 

Twin studies demonstrate a genetic aspect in people's IQ. Researchers found IQ test scores of identical twins raised together are comparable to a person's score who took the same test twice (Lykken, 1999; Plomin, 2001). The volume of gray and white matter and the function and structure of identical twins' brains are all similar (Deary et al., 2009). Music, math, sports intelligence (Vinkhuyzen et al., 2009), and linguistic and spatial intelligence (Thompson et al., 2001) were all similar among twins.


Among adopted children, mental similarities with their adoptive families are apparent in childhood (McGue et al., 1993). As they grow older, these similarities wane as experiences accumulate, and they become more like their biological parents, exhibiting genetic influences on intelligence. During childhood, estimates in heritability of intelligence is about 30 percent increasing to over 50 percent in adulthood (Deary et al., 2009).

Environmental factors include family (parents' educational background and culture, home environment, income, parent-child relationships), education, nutrition and physical activity, and place of residence.

Final Influences on Intelligence Quiz

Question

Which statement is true about genes and intelligence?

Show answer

Answer

There is no one specific gene that can control intelligence levels.

Show question

Question

The gene that helps stimulate brain pathways is involved in many cognitive activities.

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Answer

CHRM2 gene

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Question

In twin and adoption studies, around ________ of differences in IQ account for genes.


Show answer

Answer

40-80%

Show question

Question

Which statement is false?


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Answer

Adopted children and their adoptive families have a high correlation in IQ scores.

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Question

According to twin and adoption studies, which statement does not show evidence of environmental influences on intelligence?


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Answer

Identical twins raised in the same rearing environments display significant differences in IQ.

Show question

Question

Which is not a biological influence on intelligence?


Show answer

Answer

Brain processing

Show question

Question

There is a link between intelligence and cortical thickness of which two types of brain lobes?


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Answer

Temporal and frontal lobe

Show question

Question

This lobe focuses on memory and verbal and non-verbal learning.


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Answer

Temporal lobe

Show question

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This lobe focuses on executive functioning, such as planning and organizing.

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Answer

Frontal lobe

Show question

Question

Which is not a cultural influence on intelligence?


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Answer

Home environment

Show question

Question

Parents' educational background can influence children's intelligence in the following except:

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Answer

Pressuring children to be like them

Show question

Question

These are the elements of a home environment that can contribute to lower IQ scores except:


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Answer

Stimulating environment

Show question

Question

What is true about parent-child relationships concerning intelligence?


Show answer

Answer

A child's intelligence increases when he feels loved and cared for by his parents.

Show question

Question

Which two factors in education can influence intelligence?


Show answer

Answer

School attendance and length of schooling

Show question

Question

_______ is a syndrome resulting from the intake of alcohol during pregnancy marked by mental decline, language delays, and poor motor coordination.


Show answer

Answer

Fetal alcohol syndrome

Show question

Question

Which 2 genes have the strongest association with intelligence and a role in apoptosis according to a study by Sniekers et. al (2017)?

Show answer

Answer

The FOXO3 gene and CSE1L gene.

Show question

Question

True or False: Both genetic and environmental influences can affect intelligence. 

Show answer

Answer

True

Show question

Question

What are some consequences of fetal alcohol syndrome? 

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Answer

Mental decline, language delays, and poor motor coordination.

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True or False: Children who engage in physical activities tend to have higher IQs.

Show answer

Answer

True

Show question

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True or False: Cultural influences on intelligence include brain structure and volume.

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Answer

False

Show question

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 True or False: Genes have a more significant impact on cognitive differences than environmental influences

Show answer

Answer

True

Show question

Question

Which of the following has not been linked to intelligence?

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Answer

The parietal lobe

Show question

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True or False: People with higher IQs use more brain capacity to work on tasks efficiently.

Show answer

Answer

False

Show question

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True or False: Higher family income can have a positive impact on a child's IQ.

Show answer

Answer

True

Show question

Question

True or False: Beastfeeding is associated with higher IQ. 

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Answer

True

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