Environmental Factors Impacting IQ Scores

Introduction

This session focuses on environmental factors affecting adult IQ scores, complementing the previous lecture on genetics.
Topics include the Flynn effect and considerations beyond IQ measurements for life outcomes.
Discussion on the appropriateness of IQ as a measure.

The Interplay of Genetics and Environment

Genetics are important for intelligence, but the environment also plays a crucial role, interacting with our genes.
Brains don't exist in a vacuum but within the body's wider physiological environment.
Genes linked to health outcomes also appear to be linked to intelligence.
Our bodies exist within the context of the environment, further influencing cognitive development.

Cognitively Stimulating Environments

A cognitively stimulating environment optimizes the development of problem-solving skills and cognitive processes.
This includes opportunities and skills like reading, not just formal education.
Enriching and challenging environments during formative years push cognitive development to its maximum capacity.

Equal Opportunities and Systemic Biases

We need to consider equal opportunities for children to access enriching environments.
Awareness of systemic biases in society is crucial, as these can impact cognitive development.
This is particularly important when evaluating IQ scores, considering the dark history of intelligence research.

Factors Maximizing Health and Cognitive Outcomes

Good nutrition, medical care, and prenatal care are important for both physical health and cognitive development.
Avoiding adversity and trauma during critical developmental periods is crucial.
Charles Nelson's 2020 paper discusses critical periods in cognitive development susceptible to disruption from adversity and trauma.

Environmental Toxins and Societal Differences

Avoiding environmental toxins and pollutants is important for both physical and cognitive development.
Preventing children from growing up near highly toxic environments is essential.
Societal differences, such as access to technology and education, also play a role.

Sea Hero Quest Study

Focus on the structure of our environment and its impact on cognitive development.
The Sea Hero Quest study shows that the complexity of the street network affects later cognitive function.
DNA plays a role in cognitive development, but other factors interact with genes.
Sea Hero Quest collects data on spatial navigation ability through a game.

Gender Differences and Economic Wealth

Large gender differences were found in spatial navigation ability, with males outperforming females.
The effects were related to the economic wealth and gender inequality of the country.
Evidence suggests that the type of society impacts spatial ability.

Structure of the Environment

The structure of the environment we grow up in influences adult spatial navigation abilities.
The complexity of the street network is labeled as entropy.
High entropy: complex street network (e.g., London).
Low entropy: simplistic, grid-like street network (e.g., New York City).

Findings on Street Network Entropy

The entropy of the street network where people currently live wasn't consequential.
The entropy of the street network where people grew up did matter.
People who grew up outside of cities performed better on spatial navigation tasks.
People are better at navigating environments topologically similar to where they grew up.
- Example: People who grew up in low street network entropy environments such as Chicago tended to be better at video games where there was a regular layout. People who grew up in high street network entropy environments, such as Prague, tended to be better at games where there was more complexity in the street network.

Impact on Higher-Order Cognition

The physical shape and structure of our environment during critical developmental periods impacts higher-order cognition, such as spatial navigation, into adulthood.
Environmental factors, wealth of a country, gender inequality, the physical layout of where we grow up influences the shaping and impact on cognitive development.

Birth Order Effect

First-born children tend to have a cognitive advantage over later-born siblings. This is called the birth order effect or the first-born advantage.
Parental behavior shifts as the number of children increases, with parents becoming more relaxed or having less time for each child.
Resources, including parental time and financial resources, are spread more thinly with more children.

Large-Scale Studies on Birth Order

To see the first-born advantage, it's necessary to look across large groups of people or families.
Restricting analysis to families with the same biological parents helps control for genetic influence.
First-born children tend to have a specific cognitive advantage over their siblings.

Hypothesis on Environmental Changes

The hypothesis is that systematic shifts in parental behavior and the home environment impact cognitive development.
Environmental changes impact the cognitive development of the child with respect to their birth order.
Non-cognitive differences can help understand what environmental factors play a role.

National Longitudinal Survey of Youth

A nationally representative sample of about 13,000 American young people was interviewed. This study was called the National Longitudinal Survey of Youth.
Follow-up surveys gathered information on employment, income, education, and other background variables.
Child surveys included information on non-cognitive and cognitive assessments, prenatal investment, and the quality of the home environment.

Findings on Later-Born Siblings

Later-born siblings were not disadvantaged in their health or developmentally.
Parents were unable to provide later siblings with the same level of cognitive support.
Systematic differences in maternal behavior during pregnancy and the first year of life were observed.
Later-born siblings scored lower on cognitive tests, with the gap increasing until school entry.
Variations in parental behavior, such as cognitive stimulation, explained a large portion of the birth order differences in cognitive abilities before school entry.

Early Life Nutrition

Cognitive stimulation and enriching environments matter to cognitive development.
Early life nutrition is another important factor to look at.
There seems to be a general consensus that there seems to be a benefit to intelligence in adulthood as a result of breastfeeding, as a function of where and how they are breastfed.

Breastfeeding Duration and Cognitive Development

The study by I'm Gilson Angell published in 2001 looked at children breastfed for less than three months relative to those breastfed for at least six months.
At 13 months, subjects were administered the Bayley scale of infant development to give them a mental index score. At 5 year of age, the Weschler Preschool and Primary School of Intelligence (WISC). From that, they got an IQ score.
Children breastfed for less than three months were at increased risk of falling below the median value for IQ score on both tests relative to those breastfed for six months plus.
The study by I'm here published just a year after that, broken it down into more tiny things. So it looked at babies who were breastfed for less than a month, 2 to 3, 4 to 6, 7 to 9, and then nine plus.
A study broke down breastfeeding duration and considered potential confounders like social status, parental education, maternal height, and cigarette consumption.
IQ scores were higher for those who'd been breastfed for longer when confounding factors were controlled for.

Brain Development and Breastfeeding

A 2013 study found that infants who'd been solely breastfed showed improved receptive language skills and enhanced development in key areas of the brain.
Improvements were most prominent in infants who were breastfed alone.
The amount of time children had been breastfed correlated with the myelin content in their brains, particularly in areas associated with higher-order cognition.
Myelination allows signals in our brain to transfer to pass on quicker between neurons, which explains why the amount of time that children had been breastfeed for correlated with the myelin content in their brains.

Global Differences in Breastfeeding Rates

Rates of breastfeeding vary dramatically across the world.
The proportion of infants born who receive any breast milk is particularly low in the UK and Ireland relative to other countries.
The number of children who are breastfed beyond 12 months, is particularly low in the UK and Ireland relative to other countries.

Real-Life Consequences of IQ Benefits

A 2015 study in Brazil looked at long-term real-life consequences of any IQ benefit associated with breastfeeding.
Participants aged 30 were given data on how long they'd been breastfed for.
Those breastfed for more than 12 months had a 3.76 IQ point advantage over those breastfed for less than one month.
That advantage related to having spent one more year in education and earning a higher monthly income at age 30.

Mechanisms of Breast Milk Benefits

Breast milk could be supporting optimal brain development by encouraging myelination.
It could be supporting infant and child health by providing a healthy physiological context.
Breast milk might be providing optimal nourishment in those early years, supporting optimal brain development as a result.
Breast milk could be one factor in supporting child health and facilitating optimal brain development.

Breast Milk as Personalized Medicine

Studies suggest breast milk might act like personalized medicine for the infant.
When the child was unwell but the mother was healthy, the breast milk indicated an increase in the immunomodulatory constituents for fighting infection. These include CT4, T cells, and macrophages.
The breast milk seems to be upregulated in response to the health of the child, increasing the immune response.

Factors Affecting Optimal Cognitive Development

Very low birth weight might put some downward pressure on IQ scores.
Concerns were raised about the impact of having a general anaesthetic in early life on later cognitive outcomes
Having chemotherapy in early childhood on IQ has also been raised with concerns that there could be adverse effects.
Growing up living near a toxic waste site has shown negative effects in relation to impacting later cognition IQ scores.

The Flynn Effect

The Flynn effect is the substantial gains in IQ scores across successive generations in the 20th century as described by James Flynn.
IQ tests may be measuring how modern we are rather than how smart we are.
IQ gains are specific to subsets of intelligence tests that tap into fluid intelligence.
Timescales differ as the Flynn effect occurred earlier in developed countries and is now leveling out or reversing.
In some developing countries, it is still developing.

Material Explanations for the Flynn Effect

What many researchers have done is to look at the time period in which you do see this strong fluid effect and look at what else might have changed at the same time.
Significant decrease in family size (e.g., from 9.2 to 6.7 people per family).
Improved protein intake in their diet.
Decreasing in the number that showed diseases like hookworm.
Improved education was also happening at the same time, we understand formal teaching alone can't explain that change.

Material Explanations and Nutrition

Increase in physical health, then has a knock-on for IQ could be occurring is a result of improvements in nutrition and health.
This could be what is influencing improvements in IQ because this may include reduced stresses as well.
Those stressors include a more recent decrease in nutritional value in diets of countries in the West.

Theories Discredited

Genetic theories such as increased immigration or that genetic changes were affecting cognitive development have now been disproved
Causal factors underpinning the Flynn effect and the anti-Flynn effect must be environmental in nature because of studies done to compare the development genetically of one family member or birth order.
DNA genetics does not necessarily change at the individual familial level in a way that is significant.
That there isn't really an adequate reasoning is causation between family differences and causation from familial makeup to change what has been shown can have environmental causes.

Nature vs. Nurture

DNA that we inherit from our parents plays an important role in determining our IQ, and it interacts with our environment.
The environment interacts with our biology to influence our intelligence.
Intelligence might be influenced by genetics, the environment, and gene-by-environment interactions.
Always be mindful of the history of the intelligence literature and where it starts getting into dodgy ground.

What We're Measuring When We Measure Intelligence

IQ tests involve multiple tasks measuring different abilities.
We might consider what the benefits are of having a higher IQ.
IQ is important in learning and is predictive of someone's educational attainment.
Though intelligence seems to be related to occupational success and income: prior educational attainment can be a better way to predict said outcomes.
There is an unfounded and moderate relationship between IQ and achievement, and personality is also implicated in how strong that relationship is, such as people that have scored higher consciousness values and have no neuroticism values.

Factors Interacting with IQ

Intelligence is more related to school performance when students have higher levels of sustained attention.
Intelligence was associated with higher academic performance in those with higher ability, but not in those with lower ability.
Those with higher intelligence scores tended to be the ones with steeper learning curves.
We see interrelations between IQ, performance in reading comprehension, maths ability, and science understanding.
What are the real world outcomes of these measures that we're taking?

Working Memory and IQ

Working memory features heavily in IQ batteries and is very predictive of different academic outcomes.
Are we comparing apples and oranges here?
Other people build on this finding, so people like Colin that measure mental speed and measure data and then measured attention.
Maybe it's this additional skill of attention control that links these two constructs, then has this potential and effect. How are we understanding it?

Intelligence and Success

Intelligence seems to be doing something important when we think about real-world outcomes like achievement.
Perhaps, maybe the fact that one goes through the other, does intelligence moderate some other relationship that exists between maybe working memory or achievement or some other underlying construct and another real-world outcome?
If you can improve intelligence, there may be positive world effects, but it requires understanding of precursor relationships to outcomes.