The 2006 edition of Assessing adolescent and adult intelligence by Alan S. Kaufman and Elizabeth O. Lichtenberger reports correlations of 0.86 for identical twins raised together compared to 0.76 for those raised apart and 0.47 for siblings.[50] These number are not necessarily static. When comparing pre-1963 to late 1970s data, researches DeFries and Plomin found that the IQ correlation between parent and child living together fell significantly, from 0.50 to 0.35. The opposite occurred for fraternal twins.[51]
Another summary:
Same person (tested twice) .95 Identical twins—Reared together .86 Identical twins—Reared apart .76 Fraternal twins—Reared together .55 Fraternal twins—Reared apart .35 Biological siblings—Reared together .47 Biological siblings—Reared apart .24 Unrelated children—Reared together—Childrens .28 Unrelated children—Reared together—Adults .04 Cousins .15 Parent-child—Living together .42 Parent-child—Living apart .22 Adoptive parent–child—Living together .19[52]
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timeasmymeasure
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Date: 2013-11-01 05:50 pm (UTC)The 2006 edition of Assessing adolescent and adult intelligence by Alan S. Kaufman and Elizabeth O. Lichtenberger reports correlations of 0.86 for identical twins raised together compared to 0.76 for those raised apart and 0.47 for siblings.[50] These number are not necessarily static. When comparing pre-1963 to late 1970s data, researches DeFries and Plomin found that the IQ correlation between parent and child living together fell significantly, from 0.50 to 0.35. The opposite occurred for fraternal twins.[51]
Another summary:
Same person (tested twice) .95
Identical twins—Reared together .86
Identical twins—Reared apart .76
Fraternal twins—Reared together .55
Fraternal twins—Reared apart .35
Biological siblings—Reared together .47
Biological siblings—Reared apart .24
Unrelated children—Reared together—Childrens .28
Unrelated children—Reared together—Adults .04
Cousins .15
Parent-child—Living together .42
Parent-child—Living apart .22
Adoptive parent–child—Living together .19[52]