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Human Diversity > Week 4: Intelligence > Flashcards

Week 4: Intelligence Flashcards

1
Q

Galton - Eugenics

A

Eugenics is the scientifically erroneous and immoral theory of “racial improvement” and “planned breeding”

believe inheritance is purely inherited

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2
Q

Fluid intelligence (Cattell)

A

Primary reasoning ability that is free from cultural influences

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3
Q

Pattern of cognitive aging and intelligence

A

Both increase steeply in childhood

  • Crystallised abilities continue to rise for many years (env influence)
  • From the mid-twenties, fluid intelligence declines
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4
Q

Deary et al. (2013): stability of intelligence

A

r = .54 between IQ measured at age 11 and age 90

	➢ One of the most stable behavioural traits 

	➢ One of the biggest predictors of being smarter in old age is being smart at a young age

➢ Correlation is not 1 (not a perfect predictor)

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5
Q

Estimates of heritability

A

A heritability of 50% means that genes explain 50% of the variation in intelligence in the population

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6
Q

Methods to study heritability

A
  • Family studies – Assess resemblances between family members on characteristics of interest as a function of their degree of relatedness
    • Twin studies – Behaviours are compared across monozygotic (MZ) and dizygotic (DZ) twins as a naturally occurring manipulation of shared genetic makeup
    • Adoption studies – Comparisons drawn between biological parents, adoptive parents and adopted children
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7
Q

Plomin et al 2004 findings, twin study and adoption study

A

As genetic similarity decreases, so do correlations with intelligence = are genetic factors to intelligence

When twins/sibling raised apart, the levels of IQ similarity are reduced = there are environmental influences

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8
Q

Plomin et al estimate of intelligence

A

simultaneous analysis of all family, adoption, and twin data showed a heritability estimate of about 50%

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9
Q

Heritability of intelligence across the lifespan: Haworth et al, 2010

A

The heritability of intelligence is not the same at different ages.

Gene-environment interaction

From childhood to young adulthood, moved from more nurture to nature!

= Intelligence is one of the most heritable behavioural traits

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10
Q

Issues with heritability of intelligence

A

Representativeness

Complexity of genetic influence

Assortative mating

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11
Q

Representativeness

A

– Adoption and twin studies make up a large proportion of the literature in this area
– Are these families atypical from the norm?
– E.g., adoption families tend to be of higher SES (criteria for adoption)
– E.g., identical twins tend to have more similar environments than dizygotic twins

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12
Q

Complexity of genetic influence

A

– We don’t know how genes produce intelligence yet; clearly not a single gene predicts intelligence
Complexity of intelligence

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13
Q

Assortative mating: Watson et al. (2004)

A

= tendency to mate with those who are similar to ourselves

	– Studied the similarity of 291 newlywed couples 
	– Measured, e.g., age, religious/political beliefs, education, intelligence 
* Correlations of couples’ IQs were around r = .40 
* Caused by the initial selection of a mate (assortment) rather than by couples becoming more similar to each other after living together (convergence)
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14
Q

Why is assortative mating a problem for heritability estimates?

A

➢ Leads to a non-random distribution of the genetic variants important for a trait as spouses will be more similar genetically than expected by chance
➢ Assortative mating increases additive genetic variance (offspring differ more from the average than they would if mating were random)
➢ Since two highly intelligent partners are more likely to produce a child who is also highly intelligent, and similarly for low intelligence, assortative mating could inflate observed similarity of intelligence in a family.
➢ May lead to biased estimates of the relative magnitude of genetic and environmental factors (e.g., Vinkhuyzen et al., 2012)

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15
Q

The brain and intelligence:

A

Intelligence associated with both structural and functional differences in the brain

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16
Q

Structural differences

A

Grey and white matter density & number of connections are structural differences

	– Brain volume 
	– Cortical thickness  – White matter connectivity
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17
Q

Functional differences

A

Functional differences are the activation when doing tasks

More efficient processing of information, in a wide network including frontal and parietal lobe

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18
Q

Do more intelligent people have bigger brains? Evolutionary pov:

A

Potts (2011)

	* Skull size (and thus brain size) increased substantially over time 
	* Larger brain = better cognition: more brain cells allow for more complex mental processing 
	* Complexity and organisation of our brains changed as well

Steepest increase in the last 1 million years

19
Q

Do intelligent people have bigger brains? McDaniel (2005)

A
  • McDaniel (2005)
    – Meta-analysis of 37 studies, over 1,500 individuals
    – Positive correlation between brain volume & intelligence of r = .33
20
Q

Do intelligent people have bigger brains? pietschnig et al. (2015)

A

– Meta-analysis of 88 studies, over 8,000 individuals
– Reported a significant, slightly smaller correlation of r = .24

21
Q

Do intelligent people have a thicker cortex?

A

Cortical thickness shows initial increase at earlier ages, followed by sustained thinning around puberty

22
Q

Shaw et al. (2006): cortical thickness and children

A

– Cortical thickness develops differently in high- compared to average-IQ children
– Cortex thickens for longer in high-IQ children, particularly in frontal areas

	➢ Intelligence is related to the pattern of cortical growth during childhood and adolescence, rather than cortical thickness itself
23
Q

Do intelligent people have better neural highways?

A
  • Areas involved heavily depend on the particular task that is used to measure intelligence
  • Intelligence suggested to be particularly dependent on a brain network that links the frontal to the parietal lobes (P-FIT: Parieto-Frontal Integration Theory; Jung & Haier, 2007)
    • Intelligence can’t be located in isolated brain areas
      – a complex network involving the whole brain is involved
24
Q

(Penke et al., 2012) better neural highways? White matter connectivity and IQ

A

White matter connectivity is correlated with IQ

Age-related deterioration of white matter tracks is correlated with age-related cognitive decline in IQ (Lövdén et al., 2014)

25
Q

Brains of higher IQ show less or more activity when completing a task?

A

Brains of higher-IQ individuals tend to show less, rather than more activity when completing a task - > more efficient processing?

26
Q

Environmental influences of intelligence

A

➢ The Flynn effect
➢ Environmental influences

27
Q

The Flynn effect

A

= the substantial and sustained increase in intelligence scores over time.

73 studies using Wechsler and Simon-Binet tests (~7,500 participants) from white Americans’ – IQ scores rose between 1932 and 1978

  • from 20 countries
  • IQ scores rised yearly across nation
    • Nonverbal tests: average increase of ~ 15 points per generation (30 years)
    • Verbal tests: average increase of ~ 9 points per generation
28
Q

The Flynn effect: Further evidence Pietschnig & Voracek (2015), meta-analysis

A
  • 271 independent samples, almost 4 million participants
    • 31 countries
      ➢ worldwide IQ gains across 1909–2013

IQ gains vary with domain:
– Full-scale IQ: 0.28 points annually
– Fluid IQ: 0.41 points annually
– Crystallized IQ: 0.21 points annually
– Spatial IQ: 0.30 points annually

29
Q

Flynn effect: recent years

A

IQ gains seem to have flattened or even reversed (e.g., Flynn & Shayer, 2018)
➢Has humanity reached ‘peak intelligence’?

30
Q

2 opposing hypotheses for explaining flynn effect

A

– Nutrition hypothesis
– Cognitive stimulation hypothesis

31
Q

nutrition hypothesis

A

Increased intelligence is part of a nurturing environment that includes increased height and lifespan, improved health, decreased rate of infant disease, better vitamin and mineral nutrition

32
Q

Cognitive stimulation hypothesis

A

Increased intelligence driven by, e.g., improved visual analysis skills, improved schooling, changes in parental rearing styles, better-educated parents, smaller families, greater availability of educational toys

33
Q

WEIRD (Henrich, Heine, & Norenzayan, 2010)

A
  • WEIRD: Western, Educated, Industrialized, Rich, and Democratic
    * A substantial part of the evidence base - including what we know about intelligence – is based on data from WEIRD countries
    * However: there is substantial variability in experimental results across populations and WEIRD subjects are particularly unusual compared with the rest of the species – frequent outliers
    * Generalisability of findings?
34
Q

Environmental influences on intelligence Neisser et al. (1996) identified four main areas

A
  1. Biological environment (e.g., prenatal environment, nutrition)
    1. Family environment
    2. School & education
  2. Culture
35
Q

Prenatal environment - Substance abuse

A
  • Mortensen et al. (2005; see also review by Clifford et al. 2012): Smoking
    – Mothers who smoked 20+ cigarettes daily late in their pregnancy were likely to have children who performed less well on IQ tests at age 18/19
    * Mattson & Riley (1998): Alcohol
    – Children prenatally exposed to alcohol may exhibit a variety of problems with memory and attention
    – Fetal Alcohol Syndrome (FAS): deficits in, e.g., abstract thinking, planning and organizing information (Kodituwakku et al., 1995)
36
Q

Nutrition: Breastfeeding

A
  • Oddy et al. (2003)
    – Children (age 8) breastfed for more than 6 months scored 3-6 IQ points higher on a vocabulary IQ test than did children who were never breastfed
    • However, maternal intelligence is positively correlated with the likelihood of breastfeeding (Der et al., 2006)
  • When controlling for parental IQ or genetics, the effect is much smaller if at all present (review by Walfisch et al., 2013)
37
Q

Socio-economic status of the family

A

SES captures income, parental education level, parental occupation and status in the community
– SES is significantly correlated with intelligence with r = 0.3 - 0.4 (e.g., Stumm & Plomin, 2015)
– SES is related to growth in intelligence (Stumm & Plomin, 2015)
– Improving SES can improve intelligence
Better access to education?

38
Q

Family size and birth order Belmont and Marolla (1973)

A
  • Children from larger families had a lower IQ (controlled for SES)
  • First-born child always had a better IQ; scores decline with rising birth order
39
Q

Birth order criticism (Kanazawa 2012)

A

However, effects of birth order are suggested to be a methodological artefact
– less intelligent parents are more likely to have more children and
– higher birth-order children necessarily come from larger families, whereas children from smaller families have greater representation among lower birth-order children
– e.g., 4th-borns necessarily come from families with 4 (or more) children, whereas 1st - borns can come either from families with 1 or 2 children or families with 5 or 6 children
- So more likely that children of smaller families have higher rank in order and IQ

40
Q

Group socialisation Judith Harris (1995)

A

Non-shared factors outside the family may be more important in developing people’s intelligence

* As children get older, they become more influenced by their life outside the family 
* Children may identify with several social groups based on age, gender, ethnicity, abilities, interests, personality etc.; and share norms with and be influenced by these groups  * Positions within in-group and rejection of out-groups influence behaviours, personality, and intelligence
41
Q

Education

A
  • Governments across the globe do the one thing that is most likely to raise IQ: send children to school
    • Ceci (1991), meta-analysis
      – Children attending school more regularly showed higher IQ scores
      – Students’ IQ scores decrease over the long summer holidays
      – Each year of schooling is associated with a rise of 2.7 IQ points
  • Cause and effect: Intelligence is likely to influence school attendance, length of schooling, and the quality of school attended (Neisser et al., 1996)
42
Q

Culture and intelligence

A

Different cultures have different conceptions (~implicit theories) of what intelligence is
* Cocodia (2014) compared cultural perceptions of intelligence in Asia, Africa, and Western cultures
* For instance, the Luo people’s (East Africa) notion of intelligence consists of 4 main concepts:
– Rieko: similar to the Western idea of academic intelligence
– Paro: practical thinking
– Luoro: social attributes (respect, responsibility, consideration)
– Winjo: comprehending instructions

* Western and Asian cultures emphasise academic ability, rural African cultures perceive practical ability as more important 
* Some Western concepts (e.g., speed when completing tasks) are unfamiliar in African cultures 
	➢ Cultural differences may affect equal access to the skills and knowledge required by IQ tests  ➢ Can we really compare IQ (test results) across cultures?
43
Q

Is IQ culturally biased?

A
  • Raven’s Progressive Matrices are often described as a culture fair or culture reduced test, as it consists of nonverbal items thereby reducing the language loading of the test
    • However, language loading is not the same as cultural loading
      – E.g., Raven’s matrices require a specific type of abstract reasoning, which may not be entirely culture fair
44
Q

Summary

A
  • Global changes in intelligence across generations
    • Several different environmental aspects can
      – positively or negatively
      – impact intelligence
    • Intelligence is malleable, intelligence is not fixed
      ➢Gen-environment interaction
      ➢Nature with nurture

Human Diversity (6 decks)

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