Nature Controls Nurture in the Development of Sexual Orientation, and Voice is Nature’s Agent

Abstract

A testable theoretical model is presented, proposing which brain parts and mechanisms are responsible for the nature and the nurture components of all human sexual orientations. The model integrates observations from humans and a wide range of animals. If validated, the model would provide a proximate explanation of the biological substrates of all sexual orientations. The basic assumptions of the model are: (1) Children learn automatically and subconsciously in non-sexual conditioning experiences cues for recognizing sexual mates. That skill emerges at puberty. (2) Adults in the child’s surroundings act as innocuous, unaware role-models that provide the learned cues for recognizing mates. (3) Voices of men and women serve as the innate, primary unconditioned stimuli (US) in that learning process. (4) The hypothalamus is the main area that elicits the signals of the unconditioned responses (UR). Those signals trigger the learning of the associated conditioned stimuli (CS) broadcasted by the role-models. (5) The amygdala, base nuclei of the Stria Terminalis (bnST) and hypothalamus play in humans similar roles to those they play in the other species. (6) The human medial geniculate nucleus (MGN) plays the roles played by the olfactory bulbs in rodents. (7) Detectors of innate primary US and activators of the unconditioned sexual responses (UR) are located in the MGN, Amygdala, bnST and Hypothalamus Axis (MASHA). The learned conditioned stimuli (CS) are recorded in the MASHA and in cortical areas. (8) The innate US-UR connections vary across three groups of children. In the first group, only men’s voices trigger the UR. In the second group, only women’s voices trigger the UR, and in a third group each voice can trigger the UR. That determines the learned cues. The first group will be attracted at puberty only to men, the second only to women, and the third group to both.