A theory about the development of sexual orientation and sexual arousal suggests that these behaviors are learned unconsciously from asexual experiences during childhood. The brain uses the pitch of the voice of people in the child’s environment for building sexual behavior patterns that emerge at puberty. After puberty, behavior patterns that were learned from sexual experiences are added to those learned from asexual experiences during childhood  .
The first distinction that a child can make between men and women is due to the difference in the pitch of their voice. When a child hears men speaking, the child’s brain picks up features of the speaking men, such as clothing, and creates from them a brain representation of the concept ‘man’. The details of the created representation reflect the environment in which the child grows. Similarly, the child’s brain creates a representation of the concept ‘woman’ from features that it has detected in speaking women.
Connections are then developed between the brain cells that represent the concepts ‘man’ and ‘woman’ and brain centers, such as the hypothalamus, that control the physical aspects of sexual activity (physical-sex-controllers). Like the formation of the concepts ‘man’ and ‘woman’, the formation of those connections is also coordinated by the pitch of the voice. In some brains, the connection is driven by high pitch; in others, by low pitch, depending on the innate structure of the auditory system and the brain. As a result, in some children, ‘man’ becomes connected to the physical-sex-controllers, and in other children, ‘woman’ becomes connected. These connectivity differences are at the root of sexual orientation and arousal that emerge at puberty.
Genetic factors and pre- and post-natal concentrations of sex hormones affect the development of the auditory system and the connections between brain cells. These structures determine how a brain internalizes external information that eventually emerges as patterns of sexual orientation and arousal. The theory is corroborated by scientific evidence, but it needs additional testing.
Underlying causes of sexual diversity
While body differences between men and women are genetic, no genetic correlates of sexual orientation were found. Pre- and post-natal concentration of sex hormones affects the development of the sex organs, but no correlation was found between the concentration levels of hormones and sexual orientation. Concentration of sex hormones may affect the libido and other emotional traits such as aggressiveness, but they do not alter sexual orientation    . No correlation was found between the family-structure of the child (mother and father, a single parent, two parents of the same sex) and the sexual orientation of the grown-up child  .
Differentiation of some brain structures has been correlated with sexual orientation. For instance, the size of the INAH-3, which is a part of the hypothalamus, a brain area that among other things controls physical aspects of sexual activity, is larger in gay men than in heterosexual men and women . The hypothalamus also reacts to certain chemical compounds in accordance with the sexual orientation of the individual    . The amygdala, a brain area involved in emotional activities such as fear, was found to be involved in sexual activities     . The inner ear shows sex and sexual orientation differentiations. The cochleae of human females are 8-13% shorter than those of males . Otoacoustic emission (OAE), which is sound generated by the cochlea in response to external sound, was found to have sex differences even in newborns, and in adult women such differences correlate with sexual orientation. Auditory evoked potentials, which are presumed to correspond to populations of neurons from the auditory nerve through auditory cortex, showed differences in mean latency or amplitude that correlate with sex and with sexual orientation of women .
Brain centers involved in sexual development
From a functional point of view, three inter-related brain centers host the mental roots of sexuality: sensory, emotional, and physical-sex-control centers. The sensory and emotional centers provide the cues of sexual orientation and arousal, and the physical-control-centers trigger and coordinate the physical activities. In addition to these centers, other centers support the activities, by handling aspects that are not specifically sexual, such as storing and retrieving information, reward, and planning.
The role of conditioning
Conditioning is an innate learning mechanism that enables animals to adopt beneficial behaviors in the environment in which they happen to live. In Pavlov's experiments, the taste of food is the innate cue that triggers the conditioning process. Events associated with that cue (e.g. a whistle) become new triggers of salivation and the feeling of gratification, which are the innate root responses. A learned (conditioned) cue may serve in subsequent events as a trigger of additional conditioning processes. For example, additional stimuli or activities that are associated with the whistle are perceived by the dog as gratifying, and are internalized as such. That is one way in which simple root mechanisms direct the development of elaborate behaviors, which consists of a variety of cues and activities. It has been demonstrated that humans can acquire new sexual cues by conditioning. 
In Pavlov's experiment, the sensation of food triggers the reactions of salivation and gratification. Food also triggers the process of learning new behaviors. The pitch of human voice is the analog of food when humans learn sexual behavior during childhood. The same way that the taste of food creates in the brain of the animal representations of targeted foods and behavior patterns for obtaining those targets, the voice of a speaker creates in the brain of a child representation of sexual attraction targets. The pitch of the voice serves as a detector of the sex of the speaker. Based on this detection, the brain of the child builds representations of ‘man’ and ‘woman’. Through conditioning, the brain then uses these representations and builds mental models of who is sexually attractive, and what activities cause sexual arousal. Based on the hardware of the auditory system and its connections to brain centers such as the hypothalamus, some children develop sexual attraction to men, and others to women.
Sexual orientation emerges at puberty. At puberty, boys and girls whose physical-sex-controllers have been innately tuned to women’s voice will be sexually attracted to women. At puberty, boys and girls whose physical-sex-controllers have been innately tuned to men’s voice will be sexually attracted to men. Boys and girls whose physical-sex-controllers have been initially tuned to men’s and women’s voice in the same amount will be sexually attracted, at puberty, to both men and women.
The mental roots
Voice is generated and detected by genetically controlled organs, which are sex differentiated. It is robust and universal – it is one of the most reliable and commonly used cues for detecting the sex of a person. The distinction between men’s and women’s voices is based on differences in sound frequencies. Those are detected and processed by the inner ear and by the auditory neural networks, which project that information to various brain areas  . It was found that concentration of sex hormones affects the development and connectivity of neural networks  , and thus the outcomes of information that they process.
The root cues of human voice are sufficient, but not necessary, for the development of sexual orientation. Other cues may also play a role. For instance, after puberty, other root cues that depend on experiencing sexual pleasures come into play. Also, in deaf children, other mechanisms, which are still unexplored, replace the reliance on sound.
In addition to sensory cues, also arousal cues contribute to the identification of targets of sexual attraction. It was suggested   that a combination of two innate emotions, fear and the feeling of safety, is a root cue of sexual arousal. These emotions are genetic, universal and robust. In general, their combination creates excitement. For example, the excitement of riding a roller coaster or driving a fast car is attributed to a combination of the feelings of fear and safety. Analysis has shown   that a common thread of many sexual fantasies and behaviors is a combination of those emotions.
In summary, the roots of sexual orientation and arousal reside in several specialized interconnected brain centers: in the auditory system, in centers such as the amygdala that handle the emotions of fear and safety, and in center such as the hypothalamus that control the physical aspects of sexual activity. Other brain areas, such as those that handle reward, memory, and planning provide general support to the specialized centers.
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