LECTURE 4- INTELLIGENCE AND GENETICS

Question 1

eugenics

Answer 1

GALTON
scientifically inaccurate theory that says we can improve the human population via selective breeding.

Question 2

STABILITY OF INTELLIGENCE

Answer 2

• Steep increase in fluid and crystalised intelligence in childhood:
• next, crystalised abilities continue to rise for many years. From the mid-twenties fluid intelligence declines.
• Individual differences in intelligence shows it is one of the most stable states from childhood to old age. =
• Deary et al., (2013) found a correlation of .54 between QIQ measured at age 11 and at age 90. This is a sig correlation showing us it is one of the most stable behavioural traits- one of the biggest predictors in being smarter in old age is being smart at a young age. However as correlation is not 1, it shows its not a fixed genetic thing but the environment also plays a role.

Question 3

heritability of intelligence

Answer 3

• Plomin et al., (2004) looked at intelligence levels in twins and siblings- MZ twins that live together= .86 correlation, MZ apart= .72, DZ together= .6, siblings together= .47, siblings apart=.24 . This shows as genetic similarity decreases so do correlations/ when twins or siblings are raised apart the levels of IQ similarity is reduced.
• Plomin et al.,(2004) – simultaneously analysed all family, adoption, and twin data showed a heritability estimate of about 50%-]
  However Large variation within the literature; heritability estimates
  of intelligence range from ~ 30% to as high as 80%
• Harworth et al., (2010)- Finds that heritability of intelligence is not the same at different ages- there is a gen, environment interaction. Throughout age there is a transition from more nurture to more nature as intelligence becomes more genetically influenced through age. Intelligence is one of the most heritable traits.

Question 4

assortative mating

Answer 4

tendency to mate with those who are similar to us.
Watson found correlations of couples IQ were around .40 (this could inflate observed similarity of intelligence in a family)
Watson et al. (2004)
– 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)

Question 5

the brain and intelligence

Answer 5

• Skull size has increased substantially over time
• A larger brain= better cognition: more brain cells allow for more complex mental processing
• McDanial (2005)- meta-analysis of 37 studies, over 1500 individuals. Found a positive correlation between brain volume and intelligence of .33
• Pietschnig et al., (2015)- meta-analysis – reported significant correlation of .24
• Cortical thickness shows initial increase at earlier ages, followed by sustained thinning around puberty (Brouwner et al., 2014)
• Shaw et al., (2006)- cortical thickness develops differently in high IQ 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 6

intelligence and neural pathways

Answer 6

Intelligence and neural highways
* P-FIT (Parietal frontal integration theory)- Jung &Haier, 2007
* P-FIT= intelligence is particularly dependent on a brain network that links the frontal to the parietal lobes.
* Penke et a;ll., 2012- white matter connectivity is correlated with IQ
* Lovaden et al., 2014- Age related deterioration of white matter tracks alongside age-related cognitive decline in IQ

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)