Sexual orientation and brain structures: A critical review of recent research

This paper critically reviews three main studies that have sought to show that there are structural differences between the brains of male heterosexuals and homosexuals. These studies have focused on three regions of the brain, namely, the suprachiasmatic nucleus (SCN), the third interstitial nucleus of the anterior hypothalamus (INAH-3) and the anterior commissure (AC). This paper exposes a number of conceptual and methodological flaws in these studies and concludes by saying that the available evidence does not support the hypothesis that the brains of male homosexuals are structurally different from those of male heterosexuals.