The probability of a man's becoming gay rises significantly according to the number of older brothers he has.The reason for this "brother effect" may be
A)that parents with many male children secretly wish for a daughter and encourage feminine behavior.
B)that a child with older brothers behaves differently to get attention.
C)that the developing brain responds to having so many males in one house.
D)changes in the conditions within the womb caused by previous male pregnancies.

Question

Quizplus · Accepted Answer

The "brother effect" is believed to be related to changes in the womb caused by previous male pregnancies. Studies suggest that a biological mechanism may be at work, such as the mother's immune system producing antibodies to male-specific proteins that affect fetal brain development. This could potentially influence the development of sexual orientation in future male offspring.

The Probability of a Man's Becoming Gay Rises Significantly According