The fact that the correlation in IQ scores between identical twins reared apart is higher than that between fraternal twins reared together suggests that intellectual development is

A) influenced more by environmental factors than by genetics.
B) affected equally by genetics and environmental factors.
C) influenced more by genetics than by environmental factors.
D) not affected by either genetics or environmental factors.

The fact that the correlation in IQ scores between identical twins reared apart is higher than that between fraternal twins reared together suggests that intellectual development is influenced more by genetics than by environmental factors. Because identical twins share 100% of their genetic material, any similarities in their IQ scores can be attributed to genetics. On the other hand, fraternal twins share only 50% of their genetic material, and any similarities in their IQ scores could be attributed to genetics or shared environments. Therefore, the fact that the correlation is higher for identical twins supports the idea that genetics plays a stronger role in intellectual development.