• Fluid and Crystallized intelligence:
  • Fluid intelligence is how easily/quickly one learns/comprehends complex tasks (AKA "IQ"). This is typically measured via Raven's Progressive Matrices
    
  • Crystallized intelligence is essentially knowledge (information that one has stored in memory, regardless of how long it took one to aquire it).
• Heritability of IQ: 57% to 73%.
  • "Genome-wide association studies establish that human intelligence is highly heritable and polygenic" - Study "Davies, G., Tenesa, A., Payton, A. et al. Genome-wide association studies establish that human intelligence is highly heritable and polygenic. Mol Psychiatry 16, 996–1005 (2011). https://doi.org/10.1038/mp.2011.85"
  • "Intelligence is one of the most heritable behavioural traits ... from about 20% in infancy to perhaps 80% in later adulthood." - Study Plomin, R, and I J Deary. “Genetics and intelligence differences: five special findings.” Molecular psychiatry vol. 20,1 (2015): 98-108. doi:10.1038/mp.2014.105
• Positive correlation between birth order and IQ (i.e. first-borns have higher IQs than last-borns)
• How health impacts IQ
• Latter-day Saints (AKA Mormons) are selecting for slightly higher IQ partners (slightly eugenic), political conservatives for slightly lower IQ partners (slightly dysgenic), and everyone else for moreso-lower-IQ partners (dysgenic). Similarly found that conservatives, in general, show a weaker selection against intelligence than do liberals.
  • Study Kirkegaard, E., Dutton, E. Will Intelligent Latter-day Saints and Smart Conservatives Inherit the Earth? Differential Selection for Intelligence in the USA Based on Religiosity and Conservatism. Evolutionary Psychological Science (2022). https://doi.org/10.1007/s40806-022-00327-y
• National IQ is the best predictor of economic growth
  • Study Francis, G., & Kirkegaard, E. O. W. (2022). National Intelligence and Economic Growth: A Bayesian Update. Mankind Quarterly, 63(1), 9–78. https://doi.org/10.46469/mq.2022.63.1.2
• The Flynn effect
  • During the 19XXs, many parts of the world experienced both fluid & crystallized intelligence score rises. The cause(s) are uncertain but suspected to possibly include:
    • additional schooling
    • improved nutrition
    • more stimulating enviroments
    • reduction in disease
    • reduction in lead-based paint
    • reduction in leaded fuels
    This effect has stopped in many developed countries, and a "Reverse Flynn effect" has been ongoing (see below).
  • Reverse Flynn Effect: Since the 199Xs, IQ scores are decreasing in Norway, Denmark, Australia, Britain, the Netherlands, Sweden, Finland, and German-speaking countries. The cause is uncertain, but may include:
    • (some or all of the) Causes of the Flynn effect have been exhausted (e.g. all lead-based paint has been removed)
    • Immigration from lower-IQ higher-TFR countries
    • Dysgenic forces/trends are increasing
    • Culture (somewhat of a catch all)
    • Decline in religion
• Qiran Zhao, Xiaobing Wang, Scott Rozelle "Better cognition, better school performance? Evidence from primary schools in China" China Economic Review, Volume 55, 2019
  • Full paper: https://fsi-live.s3.us-west-1.amazonaws.com/s3fs-public/better_cognition_better_school_performance.pdf
  • 10000 primary school students from private migrant schools in (Chinese provinces) Beijing and Suzhou, and from public rural schools in Henan and Anhui, were IQ-tested using the Raven Standard Progressive Matrices test. High rates of developmental delay (about 33% of the students have Ravens scores that are less than one standard deviation lower than an international mean). Mean Flynn-adjusted IQ Score of "88.95". Student cognition is by far the most important factor in their academic achievement.