Assume that the probability that a man is gay is about 50% if his identical twin is gay. Karl and Konrad are identical twins. However, each was adopted by a different family soon after birth. Karl is gay. What are the chances that Konrad is also gay?
A) about 5%
B) quite a bit lower than 50%
C) somewhat lower than 50%
D) approximately 50%

Question

Quizplus · Accepted Answer

While the probability that a man is gay if his identical twin is gay is about 50%, the fact that Karl and Konrad were separated at birth and adopted into different families means that there is no genetic similarity in their upbringing. Therefore, the chances that Konrad is also gay cannot be assumed to be 50%, but is instead somewhat lower than 50%. Studies suggest that the probability could be between 10-30%.

Assume That the Probability That a Man Is Gay Is