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Douglas_Knight comments on [Question] Adoption and twin studies confounders - Less Wrong Discussion

4 Post author: Stuart_Armstrong 11 July 2014 04:44PM

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Comment author: Douglas_Knight 12 July 2014 12:42:55PM 1 point [-]

Why would this make them more different? Do you think one twin wins a resource competition and the other loses? Why do you think that?

No, resource competition is an environmental influence that twins share and it makes them similar to each other and different from single births. For example, it suppresses IQ. The most extreme similarity is that it makes them more likely to miscarry, especially boys, but this confounds other measurements.

Comment author: gwern 13 July 2014 02:42:16AM 4 points [-]

Why would this make them more different? Do you think one twin wins a resource competition and the other loses? Why do you think that?

I don't understand your questions. Why would it not make them more different? The competition introduces another source of variability: what fraction of the resources a particular fetus gets. A singleton has no such randomness, since it just gets 100%, there's no competition.