m Andrea asked some really good questions aboutAn explanation of why I don't know:And now let’s remember to ask ourselves how is physiology related to the essential essence of a human ?That encapsulates the crux of the issue, not just of M vs F, but categories, humanity, a whole host of things.
What is self? What is identity?
If (an event happens that causes trauma to your brain), and you survive, are you the same person as before? That might depend on where the damage is, some people have had radical changes of personality due to brain injury, others appear unaffected, even if they have some “cognitive impairment”, “sensory impairment” or paralysis.
What about less crude effects? Just a few microgams of LSD-25 in the bloodstream can change personality. Pituitary and other glandular tumours can cause behavioural changes and may actually cause re-wiring in some areas of the brain that are particularly plastic. Post-partum psychosis is a real threat to women after pregnancy, and that’s just due to see-sawing hormone levels.
Half of psychiatry – the half that actually works – is about neurotransmitters, though some good work is being done on electro-stimulation to cause neural changes to re-wire after damage due to PTSD, and even cure some ADD and ADHD conditions. As long as the area involved is in the rather plastic cerebral cortex, not the hindbrain, such changes should be possible (and could be quite nightmarish in the wrong hands).
Let’s look at hormones. People who are about to have their hormone levels change radically and over more than a few weeks should be made aware that the brain will re-wire as the result.
The most common cause of such hormonal-induced change is puberty. The second most common cause is a first pregnancy.
A rare cause is HRT (hormone replacement therapy), especially when administered as part of a transsexual transition, but also at times as part of cancer treatment (which gives us a good baseline for a control group when studying trans people).
The changes happen fairly quickly, they are perceivable very early by the person concerned. The degree of relief or conversely discomfort caused by the first signs of them is often used to confirm or exclude diagnosis of transsexuality.
See http://www.avitale.com/TreatmentPlan.htm Stage IIIt is well documented that the administration of cross sex hormones have a mitigating effect on patents suffering from severe gender dysphoria. The effect is so marked that the treatment is used to confirm or reject the GID diagnosis. Fortunately. psychological outcomes precede permanent physiological secondary sex characteristic changes, making it an ideal diagnostic confirmation/contraindicating tool. Referral is made to a physician who is well versed in the administration and monitoring of patients taking cross sex hormones..(Parenthetically, although I’ve never had to deal with PMT every month for decades, I did have to deal with a PMT/Menopause/PMT/Menopause cycle due to uncontrolled hormone swings for several months in 2005. I’d rather not repeat the experience.)
Psychotherapy: Early Stage: Patient is closely monitored for adverse psychological effects of HRT. If no adverse effects are detected or reported and patient reports relief and wishes to continue HRT, patient is educated and prepared for psychological and physiological changes to secondary sex characteristics that are well known to result from the treatment.
Some individuals accept the physical and psychological changes brought about by HRT and incorporate them into their originally assigned gender role. Others may choose to transition to living full time in the new gender role.
Back to HRT:
There are gross changes to the size of brains that are easily measured:
Changing your sex changes your brain: influences of testosterone and estrogen on adult human brain structure by Pol et al, Europ Jnl Endocrinology, Vol 155, suppl_1, S107-S114 2006Results: Compared with controls, anti-androgen + estrogen treatment decreased brain volumes of male-to-female subjects towards female proportions, while androgen treatment in female-to-male subjects increased total brain and hypothalamus volumes towards male proportions.But we know little of the details.
Some areas don’t change. For example, trans men show male-pattern anatomy and cognitive processes before as well as after hormone therapy in some areas.
Neuroimaging Differences in Spatial Cognition between Men and Male-to-Female Transsexuals Before and During Hormone Therapy by Scoening et al J Sex Med. 2009 Sep 14.Conclusions. Our results confirmed previously reported deviances of brain activation patterns in transsexual men (sic - these are MtoF i.e. transsexual women) from men without GID and also corroborated these findings in a group of transsexual patients receiving cross-sex hormone therapy. The present study indicates that there are a priori differences between men and transsexual patients caused by different neurobiological processes or task-solving strategies and that these differences remain stable over the course of hormonal treatment.So it’s not that simple. There’s no such thing as a “male brain” or a “female brain”, any more than there’s a “male height” or “female height”. (Yet men tend to be taller than women).
Height isn’t a social construct, but the concepts of “Tall” and “Short” are. 5' 5" is tall for a woman in Thailand, short for a woman in Kenya. And tall for a man anywhere in Europe in the middle ages.
Looking at Gender… 80% or so is a social construct. It differs from place to place and time to time. Pink was a “traditionally masculine” colour in the 19th century. There are few “traditionally gendered” behaviours that have any biological basis at all, and fewer still that are strongly based on biology.
A lot of the ones thought to be based on biology – as they pretty much all were in the 19th century – aren’t. That doesn’t mean to say that none are, we have to look at the actual evidence. Mathematical ability – sexually isomorphic. Instinctive ballistics calculations – sexually dimorphic. And it’s all statistical anyway, we have to treat people as individuals.
One of the areas – or rather, clusters of areas – that is sexually dimorphic (ie boys and girls are anatomically different) is in the lymbic nucleus, which leads to different emotional responses and instincts, which leads to gender identity (or rather, sex identity) crystallisation due to socialisation.
Details over at Biased-Interaction Theory of Psychosexual Development: “How Does One Know if One is Male or Female?” M.Diamond Sex Roles (2006) 55:589–600
Theory predicts that if you bring up a standard, cis-sexual girl in a world where all the people she interacts with are non-op transsexuals, then she will identify as a trans-sexual boy. Because all the boys think, feel, emote, hear, smell etc like she does, and the girls are quite different.
I over-simplify. Because she’d get distress from taking male hormones (wrong neurology) and wouldn’t desire body modification or surgery. Her body map and body are congruent. So she’d be non-op.
Goodness knows what her sexual orientation would be. Is that a matter of pheremones and physical attraction to shape, or psychological attraction? A combination maybe? Or would the incongruence lead her to be Bi or Asexual?
I don’t know.
My own sexual orientation was asexual, and mildly lesbian before my change. Now I'm straight, with a Libido and everything. Was this the result of a removal of a psychological block, or brain re-wiring in a borderline case? Or a combination? The timing is right for the latter, but one area the specialist psych did surprise me with was her warning for me to be prepared in case my orientation changed. When it did, some 4 months later, it looks like the only one at all surprised was me. Everyone else seemed to expect it, either from ignorance of the issue, or possibly seeing signs and portents that I myself did not.
Whatever. It happened. It did leave me with a psychological aversion to thinking about the issue though, which accounts for me not researching this area as thoroughly as I might. I don't know. I should. I'd rather not go there right now though, it would distract me too much from being a parent and doing my PhD.
I try to be objective. I don't always succeed. No scientist does. The good ones realise it, and state the limits of their objectivity, so others can make proper allowances.