Lecture 4 - Intelligence 2

Question 1

What is intelligence one of the best predictors of?

Answer 1

• One of the best predictors of important life outcomes such as education, occupation, mental and physical health and illness, and mortality

Question 2

Galton and the idea of nature vs nurture

Answer 2

• Galton was the first to differentiate between the influences of nature and nurture
  
  • He observed that eminence seems to run in families
  • “[…] there is no escape from the conclusion that nature prevails enormously over nurture” (Galton, 1883, p. 241)

Question 3

what is eugenics?

Answer 3

• Eugenics is the scientifically inaccurate theory that humans can be improved through selective breeding of populations

Question 4

why is the idea of eugenics bad?

Answer 4

• The implementation of eugenics practices has caused widespread harm, particularly to populations that are being marginalized

Question 5

relationship between cognitive aging and intelligence

Answer 5

• Steep increase in both fluid and crystallised intelligence in childhood
  
  • Clear distinction in what happens next:
    ○ Crystallised (collective experiences through life) abilities continue t rise for many years
    ○ From the mid-20s, fluid intelligence (abstract thinking, problem solving) declines

Question 6

stability of intelligence across the lifespan

Answer 6

• Individual differences in intelligence show high stability from childhood to old age
• Deary et al. (2013):
  ○ Correlation of 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

Question 7

what is heritability?

Answer 7

• Heritability is a measure of how well differences in people’s genes account for differences in their phenotype

Question 8

what does a heritability of 50% mean?

Answer 8

• A heritability of 50% means that genes explain 50% of the variation in intelligence in the population
  • Heritability does not say that 50% of an individual person’s intelligence is due to their DNA. The heritability estimate is a group figure describing the reasons for the variance in intelligence among the sample of people studied.

Question 9

how can heritability be studied?

Answer 9

○ 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

Question 10

correlation results of Plomin (2004) heritability of intelligence study

Answer 10

test-retest = 87
MZ together = 86
MZ apart = 72%
DZ together = 60%
siblings together = 47%
siblings apart = 24%

Question 11

what happens o intelligence as genetic similarity decreases

Answer 11

correlations with intelligence decreases

Question 12

Haworth et al. (2010) findings

Answer 12

• The heritability of intelligence is not the same at different ages
  ○ Gen-environment interaction
  ○ Transition from (more) nurture to
  (more) nature
  ○ Intelligence is one of the most
  heritable behavioural traits

Question 13

issues with heritability of intelligence

Answer 13

• Representativeness – Adoption studies and twin studies, which both have limitations, make up a large proportion of the literature in this area
  
  • Complexity of genetic influence – We don’t know how genes produce intelligence yet; clearly not a single gene predicts intelligence
  • Assortative mating

Question 14

what is assortative mating?

Answer 14

• tendency to mate with those who are similar to ourselves

Question 15

Watson et al., (2004) study on assortative mating

Answer 15

• Watson et al.(2004)
  ○ Studied the similarity of 291 newlywed couples
  ○ Measured, e.g., age, religious/political beliefs, education, intelligence
  
  • Correlations of couples’ IQ’s 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).
    ○ Assortative mating could inflate observed similarity of intelligence in a family

Question 16

do intelligent people have bigger brains? explain

Answer 16

• Evolutionary perspective:
  ○ 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 organization of our brains changed as well

Potts (2011)

Question 17

what have advances in neuroimaging techniques enabled?

Answer 17

assessment of in vivo (living) brain volume

Question 18

McDaniel (2005) study into brain size and intelligence

Answer 18

○ meta-analysis of 37 studies, over 1,500 individuals
○ positive correlation between brain volume & intelligence of .33

Question 19

Pietschnigetal (2015) study into brain size and intelligence

Answer 19

○ Meta-analysis of 88 studies, over 8,000 individuals
○ reported a significant, slightly smaller correlation of 0.24

Question 20

evidence suggesting thicker cortex and increased intelligence

Answer 20

• Cortical thickness shows initial increase at earlier ages, followed by sustained thinning around puberty (cf. pruning; Brouwer et al., 2014)
  
  • Shaw et al. (2006):
    ○ Cortical thickness develops differently in high- compared to average-IQ children.
    ○ Cortex stayed thicker 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

Question 21

do intelligent people have better neural highways? explain

Answer 21

• P-FIT (Parieto-Frontal Integration Theory, Jung & Haier, 2007)
  ○ Intelligence is particularly dependent on a brain network that links the frontal to the parietal lobes
  § White matter connectivity is correlated with IQ (Penke et al., 2012)
  § Age-related deterioration of white matter tracks alongside age-related cognitive decline in IQ (Lövdén et al., 2014)

Question 22

do intelligent people show more efficient brain function? explain

Answer 22

• Intelligence can’t be located in isolated brain areas – a complex network likely involving the whole brain is involved
  
  • Brains of higher-IQ individuals tend to show less, rather than more activity when completing a task
  • P-FIT
    ○ Lateral frontal cortex (reasoning, attention, and working memory) seems to support fluid intelligence, but also the parietal lobe (collecting and organizing perceptual information) is implicated (e.g., Choi et al., 2008)

Question 23

what is the Flynn effect?

Answer 23

• The substantial and sustained increase in intelligence scores over time.

Question 24

the Flynn effect and intelligence

Answer 24

• Flynn(1984)
  ○ 73 studies using Wechsler and Standard-Binet tests (~7,500 participants) from white Americans’
  ○ IQ scores rose between 1932 and 1978
  • Flynn(1987,1994)
    ○ data from 20 countries
    ○ IQ scores were rising yearly across nations
  • Nonverbal tests: average increase of ~15 points per generation (30years)
  • Verbal tests: average increase of ~9 points per generation
  • Further evidence:
    ○ Pietschnig & Voracek (2015), meta-analysis
    § 271 independent samples, almost 4 million participants
    § 31 countries
    § worldwide IQ gains across 1909–2013
  • Further evidence:
    ○ Pietschnig & Voracek (2015), meta-analysis:
    § 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
    □ IQ gains have decreased in more recent decades
  • Flynn effect:
    ○ IQ scores increase over time – on a global level
    ○ In more recent years, IQ gains seem to have flattened or even reversed (e.g., Flynn & Shayer, 2018)
    § Has humanity reached ‘peak intelligence’? Nevertheless: IQ scores have changed, which makes it unlikely that intelligence is determined by genes only

Question 25

is the Flynn effect of IQ nature or nurture?

Answer 25

• Although the cause of the Flynn effect is still a matter of debate, it must be due to multiple environmental factors rather than a genetic shift.
  ○ more recent changes to IQ are unlikely the product of genetic evolution, the timescales are simply too short

Question 26

opposing theories other than Flynn effect

Answer 26

nutrition hypothesis
cognitive stimulation hypothesis

Question 27

nutrition hypothesis

Answer 27

• 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

Question 28

cognitive stimulation hypothesis

Answer 28

• 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

Question 29

environmental influences on intelligence

Answer 29

• Neisser et al., (1996) identified 4 main areas
  1. Biological environment (e.g., prenatal environment, nutrition)
  2. Family environment
  3. School and education
  4. Culture

Question 30

effect of prenatal environment of intelligence

Answer 30

• Substance abuse:
  ○ Mortensen et al. (2005): 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 and 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)

Question 31

effect of nutrition on intelligence

Answer 31

• Breastfeeding:
  ○ Oddy et al., (2003)
  § Children (age 8) breastfed for more than 6 months scored 3-6 IQ points higher on a vocabulary intelligence 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)

Question 32

effect of family size and birth order on intelligence

Answer 32

• Belmont and Marolla (1973)
  ○ Children from larger families had a lower IQ (controlled for social class)
  ○ First-born child always had a better IQ; declining scores with rising birth order
  
  • Debate around whether effects of family size and birth order are confounded

Question 33

effect of group socialisation on intelligence

Answer 33

• Judith Harris (1995)
  ○ Non-shared factors outside the family may be more important in developing people’s intelligence
  ○ As children get older they become more influence 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

Question 34

effect of socio-economic status of the family on intelligence

Answer 34

• SES captures income, parental education level, parental occupation and status in the community
  ○ SES is significantly related with intelligence with r = 0.3 - 0.4
  ○ Improved SES can improve intelligence

Question 35

effect of education on intelligence

Answer 35

• Governments across the globe do the one thing that is most likely to raise IQ: go 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)

Question 36

effect of culture on intelligence

Answer 36

• Culture as the collective beliefs, attitudes, traditions, customs, and behaviours that serve as a filter through which a group of people view and respond to the world
  • Serpell (2000): three ways in which the concept of intelligence in Western societies is set apart from other cultures in the world:
    ○ Decontextualisation – disconnecting from a particular situation and thinking abstractly, in contrast to context-dependence
    ○ Quantification – understanding and expressing something in terms of quantity or numbers
    ○ Biologisation – emphasis on biological and evolutionary theories in understanding mind and behaviours
  • Cocodia (2014) compared cultural perceptions of intelligence in Asia, Africa, and Western cultures
  • For instance, in Luo of East Africa people’s notions 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

Question 37

is IQ culturally biased? explain

Answer 37

• 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