What correlation in intelligence scores is observed for fraternal twins reared together?

a) Approximately 0.90

b) Approximately 0.72

c) Approximately 0.60

d) Approximately 0.50

c

The evidence for hereditary influences on intelligence comes mainly from studies on twins and adopted children. The intelligence of identical twins reared together correlate almost 0.90. Twins separated early in childhood also show considerable similarity in their intellectual, personality and behavioural characteristics. The intelligence of identical twins reared in different environments correlate 0.72, those of fraternal twins reared together correlate almost 0.60, and those of brothers and sisters reared together correlate about 0.50, while siblings reared apart correlate about 0.25. Another line of evidence comes from the studies of adopted children, which show that children’s intelligence is more similar to their biological rather than adoptive parents.