http://www.medical-hypotheses.com/article/S0306-9877%2812%2900062-X/abstractBetween the two extreme ends of human sexuality – male and female – lie a poorly understood and poorly studied spectrum of ambiguously defined sexual identities that are very much a part of the human condition but defy rigid classification. "Bigender" is a recently formed sub-category of ->-bleeped-<-, describing individuals who experience a blending or alternation of gender states. While recognized nominally by the APA, no scientific work to our knowledge has addressed this fascinating condition, or proposed any physiological basis for it. In addition, the alternation aspect has not been proposed as a nosological entity distinct from blending.
We present descriptive data suggesting that many bigender individuals experience an involuntary switching of gender states without any amnesia for either state. In addition, similar to transsexual individuals, the majority of bigender individuals experience phantom breasts or genitalia corresponding to the non-biologic gender when they are in a trans-gender state. Finally, our survey found decreased lateralization of handedness in the bigender community. These observations suggest a biologic basis of bigenderism and lead us to propose a novel gender condition, "alternating gender incongruity" (AGI).
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There's more to read, if you have the dosh to buy the article (I don't) - this is just the abstract. The paragraph breaks are mine, by the way.
I'm posting this here because there's very little researched or written in the academic community about bigender.__________________________________________________________________________________________________
Alternating gender incongruity: A new neuropsychiatric syndrome providing insight into the dynamic plasticity of brain-sex Medical Hypotheses, Volume 78, Issue 5 , Pages 626-631, May 2012 | Laura K. Caseemail, Vilayanur S. Ramachandran
Center for Brain and Cognition, University of California, McGill Hall, 9500 Gilman Dr. M/C 0109, La Jolla, San Diego, CA 92093, United States
Received 12 October 2011; accepted 25 January 2012. published online 24 February 2012.
Retrieved from the Internet on August 9, 2012 by SJ
http://www.medical-hypotheses.com/article/S0306-9877%2812%2900062-X/abstractBetween the two extreme ends of human sexuality – male and female – lie a poorly understood and poorly studied spectrum of ambiguously defined sexual identities that are very much a part of the human condition but defy rigid classification. "Bigender" is a recently formed sub-category of ->-bleeped-<-, describing individuals who experience a blending or alternation of gender states. While recognized nominally by the APA, no scientific work to our knowledge has addressed this fascinating condition, or proposed any physiological basis for it.
In addition, the alternation aspect has not been proposed as a nosological entity distinct from blending. We present descriptive data suggesting that many bigender individuals experience an involuntary switching of gender states without any amnesia for either state. In addition, similar to transsexual individuals, the majority of bigender individuals experience phantom breasts or genitalia corresponding to the non-biologic gender when they are in a trans-gender state. Finally, our survey found decreased lateralization of handedness in the bigender community.