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Thinking positively: The genetics of high intelligence

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136 points gwern | 5 comments | 01 Nov 15 23:33 UTC | HN request time: 0.236s | source
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dgrant ◴[02 Nov 15 16:09 UTC] No.10492622[source]▶
Can someone explain this for someone like me with no education in biology or psychology?
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kylemathews ◴[02 Nov 15 16:27 UTC] No.10492785[source]▶
The researchers did a study of Swedish military conscripts (98%) of male population. They tested if high-intelligence is as inheritable as general-intelligence. They found strong evidence that it does as siblings of high-intelligent soldiers also tended to more intelligent than the norm.
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1. ambicapter ◴[02 Nov 15 17:12 UTC] No.10493187[source]▶
How does that show anything. Can't you assume that siblings would be raised in similar environments?
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2. themetrician ◴[02 Nov 15 17:17 UTC] No.10493252[source]▶
Similar levels of intelligence have been seen even in switched-at-birth twin cases where one twin is raised by one family and another by another. The IQ between the twins was in every case more correlated than the IQ of each twin and their family-siblings. Look up the interview with Nancy Segal on YouTube about Twin Studies and IQ.
3. bpodgursky ◴[02 Nov 15 17:49 UTC] No.10493579[source]▶
Why is the comment by themetrician dead? (sibling to comment here) I don't understand.
4. femto113 ◴[02 Nov 15 18:38 UTC] No.10493972[source]▶
They controlled for environment by considering the difference between non-twin siblings (< 2 years apart in age), fraternal (two-egg) twins, and identical (single-egg) twins. The correlation in intelligence between non-twin siblings and fraternal twins was similar, and both are significantly lower than the correlation between identical twins. The most plausible explanation for this is the genes that identical twins share.
5. vox_mollis ◴[02 Nov 15 19:13 UTC] No.10494273[source]▶
Nearly every twin study done in the history of twin studies has demonstrated minimal effects of shared environment on outcomes.