The intelligence of fraternal twins raised in the same home is more similar than the intelligence of nontwin siblings raised in the same home. This finding provides evidence for the effects of environment on intelligence because fraternal twins and other siblings have the same degree of genetic relatedness.

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Quizplus · Accepted Answer

This finding suggests that environmental factors rather than genetics play a greater role in the development of intelligence. Since fraternal twins and other siblings raised in the same home have the same genetic relatedness, any differences in intelligence between them are likely due to environmental factors such as parenting, education, and nutrition.

The Intelligence of Fraternal Twins Raised in the Same Home