lec 10. nurture and intelligence

Factors of nurture that could affect intelligence

Is the environment cognitively stimulating enough to develop intelligence ?

Equality opportunities across society?

Optimal health (good nutrition, medical care etc)

Avoiding adversity / trauma

Avoiding environmental toxins/ pollutants

Spatial navigation and structure of environment

Sea hero quest – spatial navigation activity

-              Found males performed better than females in almost every bracket

-              Effects related to economic wealth of country

-              Gender differences related to gender inequality of the particular country

-              Society we grow up in impacting spatial ability

Street networks and spatial navigation

London -> more complex street networks – higher entropy score

New York -> Less complex street network – low entropy score

-              Self report where grew up and where live now

-              Where they currently live didn’t impact spatial ability much

-              But where they grew up did impact

-              More complex street network -> better spatial ability

-              Also found they were better at navigating environments similar to where they grew up

Birth order effect

-              Findings that first borns have a cognitive advantage than siblings

-              Due to parents becoming more relaxed, less time to spend etc, financial resources

• systematic shifts in parenting and home environment

National longitudinal survey of youth

American youths first interviewed in 1979

Completed surveys on employment,income, education etc

In 1986, children of the females from original sample were interviewed bi anually

Child surveys included birth outcome, early childhood parental investments, etc as well as cognitive development information

National longitudinal survey of youth Findings

-              Later born children not disadvantaged in health or developmentally

-              But parents are unable to provide them with the same level of cognitive support as they do with first born

-              Systematic differences in maternal behaviour during pregnancy and in first year of life

-              As early as 1yr of age, later born children score lower than siblings

-              This gap increases until school entry and remains significant thereafter

Angelson - breastfeeding and cog development

children breastfed for less than 3 months had an increased risk compared to children breastfed for at least 6 months of a test score below median value on infant development (at 13 months) and IQ (at 5 years)

Mortenson breastfeeding and IQ

included 13 potential cofounders as covariates. Found those breastfed for 7-9 months and 9+ months had higher iq than those breastfed for shorter durations

Breastfeeding and myelination - deoni

Myelin allows signals to transfer quicker between neurons

Deoni 2013 – found myelin content in brains correlated with breastfeeding duration, particularly brain areas that are associated with cognition

Victoria - breastfeeding and cognitive development long term

Victoria  2015 – long term consequences on Iq,years of schooling and income at age 30yrs. Information on IQ and breastfeeding

Results – those who had been breastfed for more than 12 months had 3.76 IQ point average – not a massive advantage but still significant

Being breastfed for longer spent more time in education and earns higher monthly income at age 30

Breast milk and health of child

When healthy mother feeding unhealthy infant – increase in immunomodulatory constituents in breast milk, particularly ct4 T cells and macrophages , important for fighting infections

Increase in immune response so infants benefit

Breast milk sees to be upregulated in response to health of child and provides child with helpful, positive constituents

Powls and Cooke - low birth weight and IQ

Powls and Cooke – looked at children who had been born with a low birth weight and then estimated IQ when 13 – children with low birth weight score on an lower average for IQ scores

What is the Flynn effect

If look at IQ scores across generations, substantial gains

Iq progressively increasing with generations

In 1900, 3% of Americans were lawyers, doctors, teachers

Today 35% practice cognitively demanding professions across a whole range

Professions and science have upgraded

Hypothesis that iq tests are testing how modernised we are rather than how smart we are?

Iq gains specific to subsets of intelligence tests that tap into fluid intelligence as opposed to crystallised intelligence

We don’t see gains across the crystallised intelligence subtests

We see Flynn effect in developed and developing countries but it occurred earlier in developed countries

Does generally appear at times where countries become more standardised in terms of formal education

Anti Flynn effect

Significant decline in IQ – anti Flynn effect

Evidenced in a few studies

But not evidenced in those developing countries where we are still seeing Flynn effect

Interpreting Flynn effect - materials

Looked at time periods at strong Flynn effect in particular country and what else changed at same time

Rural Kenya study – 1984-1998

Found a significant decrease in family size – went from average of 9.2 people per family to 6.7 per family

Individuals energy intake in terms of calories also improved and so did protein intake

Diets becoming more nutritious, more food available in these time periods

Does the material hypothesis explain the anti Flynn effect

Hard to explain how it would explain the reverse

Material explanations -> evidence that nutrition has worsened, changes in education

The anti Flynn effect is not well understood but the material hypothesis can account of the Flynn effect and the anti Flynn effect

Alternative explanation for anti Flynn

More intelligent people having fewer children

This was discredited by bratsberg and rogeberg 2018. - found effects to be there when just look at family generations and siblings