For science!
Drops a Sweet Katana said:
Effectively, someone who's transgender has a brain of one sex in the body of the other (for example a 'male' brain in a female body). From my understanding, it's caused by a mismatch of hormones in the body, specifically a mismatch of the hormones produced by the genitalia and the hormones required for the brain to function. Since the male and female brain require different hormone balances to function properly, having the wrong hormone production can lead to some pretty shitty psychological effects that makes life more than a bit crap for person in question.
The "hormones" which allow the brain to function are called neurotransmitters, and aren't generally counted as hormones (although they're structurally very similar) because they only travel a very short distance from where they are produced to the receptor site. This is important because neurotransmitters have to convey information very fast.
The issue with your theory is that neurotransmitters are produced by neurons (the cells in your brain) which are the same whether you are male or female. While there is evidence that sex hormones influence the production of neurotransmitters, this is mostly a short term thing. If your level of sex hormones suddenly changes (i.e. if you're going through a menopause or taking hormone supplements) it can cause very extreme changes in how your brain works (and particularly your mood). Over time, however, neurons will simply adapt to the natural level of sex hormones in your body and produce the amount of neurotransmitters your brain needs to keep working.
Furthermore, neurotransmitters could not explain the cognitive effects of feeling that your brain and body don't match. If it was simply that trans people were generally depressed all the time, sure, but it wouldn't explain why gender identity was the focus since a person wouldn't be consciously aware that their issues were due to sex hormones. This also wouldn't explain why trans people tend to fare so much better emotionally when they start living as the sex they identify with. If it was simply that their hormones were out of line, then the hormone state would not have changed just because their lifestyle has and therefore we would not expect any improvement.
Lunncal said:
My understanding of it is that people actually have kind of an innate internal blueprint of how their body is "supposed" to be, and sometimes this doesn't match up with what their body physically is, which causes all kinds of issues.
The issue with the comparison to a phantom limb is that it's only found in amputees. People who are born without a particular limb don't have it.
The issue there is that the brain has essentially "learned" over its lifespan to expect certain forms of neurological feedback. As your nervous system develops, your brain adapts itself to the task of controlling and receiving information from all your limbs. It's why it's so difficult to build a prosthetic limb which a person can control with their nervous system, because the way the brain "organizes" that information is unique to the individual and learned over their life.
When the limb is suddenly lost, even if the mind consciously accepts the loss the neurology of the brain doesn't know how to respond. It's set up specifically to organize all this information which it expects to be receiving but is not getting any more.
There's a much more interesting theory which is similar to what you're suggesting called "cognitive prototyping". Basically, the theory is that human beings are intensely neurologically geared around recognizing other people, particularly their faces. It's one of the first cognitive tasks which babies are able to perform and they can do it from as little as a few hours after birth. It's possible that during that time the baby has already developed a "prototype", an understanding of what a face is meant to look like based on a synthesis of different faces it has seen, and there's some evidence to suggest that babies can already distinguish between "male" and "female" faces from only a few days after birth.
Whether this has anything to do with how a person develops
personal identity though is another matter. Babies don't have any of the hallmarks of personal identity, they don't seem to recognize themselves in mirrors until quite a while after they've already learned to recognize faces, for example. It's likely that identity formation is actually a very long process and probably a very complicated one.
In short, I'd be extremely, extremely wary of concluding or even suggesting that being trans is caused by a single thing. There is no single explanation which holds up and can account for all possibilities, and much as people tend to get excited when a researcher reports some bold claim about sex differences in the brain or prenatal hormone profiles, it's worth being conservative about just how much explanatory value these theories have given quite how many different, incompatible (and in many cases, defunct) notions have been put forward as "the" cause of gender identity over the years.