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Q. How and when does templating for sexual orientation occur in the brain?

A. Research is not yet sufficiently advanced to specifically describe in detail how and when sexual orientation is templated in the brain. What is clear is that the developing fetal brain does undergo templating (gender-patterning) for aspects of human sexuality including sexual identity, orientation, and preference. Nature plus nurture results in an individual’s personal sexual template.

During gestation, templating for sexuality appears to involve a region in the anterior hypothalamus; the INAH3 (the Third Interstitial Nucleus of the anterior hypothalamus) more specifically. This hypothalamic nucleus is on average more than twice as large in the brains of heterosexual males than it is in the brains of females or homosexual males. Critical time periods likely involve the last part of the first trimester and/or the 16 th-26th weeks of gestation. Templating may occur atypically if something interferes with any or all of the process. Research continues in this area. Dorner, Diamond, and Seligman are three individuals who have taken a position on this process. Each has his own way of describing templating.

Dr. Gunter Dorner, a German scientist, said templating of the brain for sexual identity and related behaviors occurs through the development of three centers:

Dr. Milton Diamond, an American scientist, said four stages of development are likely to be involved:

Martin Seligman, PhD, author of the book What You Can Change...and What You Can’t, defined five layers related to human sexuality and templating:

According to Dr. Seligman the ability to change and/or the ease with which a person is able to change is related to the depth of the layer (e.g., the deeper the layer the more difficult it is to achieve change). Thus the core layer is the most resistant to any type of change while sexual performance is the easiest to alter, even though the process may be difficult and painful. He also made the point that while some can learn to exhibit a variety of sex-related behaviors (e.g., can engage in sexual relations with another person through the use of fantasy), the individual’s core identity and orientation toward the type of person he/she wants to be sexual with are likely to remain constant.

You may want to refer to Brain ReferencesSexuality and the Brain for additional brain facts.