Like similar studies on younger twins, the study has revealed the importance of genes in cognitive ability throughout life, he said.

The mother had been brought to the Manchester hospital because it has a medical unit that specializes in operating on joined twins.

She was called to render an opinion on 8-year-old twins whose teacher felt they should be apart and transferred one to another class.

Dr. Carson's earlier efforts on other twins did not go as well.

Lykken was also known for his work on twins, which he began in 1970.

The Dallas neurosurgeons had never operated on such twins before.

You read the literature on identical twins - one personality in two different bodies.

Evidence from studies done on twins indicates that genetic factors may play a role in determining a person's personality.

Did you see that New Yorker piece on twins by any chance?

Still, while the data has problems, it is piling up - there are at least seven studies on twins.