What condition is required to hold true the research finding that men are more likely to have a same-sex affectional orientation if they have older brothers?

Question

Quizplus · Accepted Answer

The research finding that men are more likely to have a same-sex affectional orientation if they have older brothers is associated with the "fraternal birth order effect," which does not specifically require right-handedness, older sisters, color blindness, or high testosterone to be true. However, the effect has been observed to be stronger or more consistent among right-handed individuals, making right-handedness a relevant condition in the context of how this question is framed, despite it not being a direct requirement for the fraternal birth order effect itself.

What Condition Is Required to Hold True the Research Finding