Maybe there's gender inside your head, maybe there's not. I don't know. There's probably some gender inside my head, but it matters precious little in my everyday life. What matters, hugely, is gender other people ascribe to me, you and aunt Tillie. Most people don't seem to care about identities at all - they just slop a gender on you, and if you're lucky, it sorta kinda fits, and if you're unlucky, it's a match made in hell - not only does it not fit, but other people are hell-bent on making you fit the gender.
A big part of gender lives in the perceptions of other people.
I think that's often missed in queer studies: the preferred position seems to be looking in, not out. Prominent questions being gender identities (how do you feel, on the inside?), gender presentation (how do you like to present yourself? - instead of asking myself why do I see you the way I do?), gender transgression (how/why do you transgress? - instead of why do I see the way you are as transgressing?).
The point of view is from an unknown, "neutral" observer to a queer "subject" - but the questions asked, and the answers given to them betray something else entirely: it's the observing subject that gets to ask the questions, and it's not the observing subject that questions hirself, or sees hirself as a subject, even - that bit of subjectivity is, more often than not, entirely hidden from view. It's replaced with a "subjectivity" (within very strict limits - questioning of the questioner is definitely not allowed) for the queer transgressor and a mock objectivity for the "neutral" observer. For samples, go read almost any of the big names: Butler, Foucault, Sedgwick, Halberstam - the list goes on and on. These people tell almost nothing of themselves yet proceed to dissect queer lives from a supposedly neutral standpoint of academia.
Well, I beg to differ. It seems to me gender is made by the observers. It's not entirely independent of the observations, but there's a lot of room for interpretation of observations, and this room is used by the observers to build, model and create gender - and this is the but that interests me greatly. It's also a bit that, AFAIK, hasn't been studied much. I'd call it the hermeneutics of gender (well, being the Gadamer-loving humanist I am, this is hardly a surprise). Why do we see the things the way we do is, in my opinion, the crucial question.
This point of view has also the helpful effect of removing the onus of being observed from us trans/queer/whatever people. It's not us. It's the people questioning us that really need to be questioned.