I considered myself transgender earlier on in life, but pushed it out of my mind as just as phase or something I was going through, but now it's back in the forefront of my mind just like it was before. I could just repeat the sex/gender dichotomy stuff that many people have posted, but I'd rather focus on something different. Personally, I'd like to see gender lines continue to blur, and have an expansion of both genders' expected roles. I just think that would be a good thing for humanity.
I also feel like even within the gay and trans community there's such a tendency to group people into one of two categories, which I don't think is healthy or good whatsoever. I mean, there is androgyny and gender identities that fall outside the dichotomy, and I feel like those get lost in the flux sometimes. I've felt like I belonged in a female body for a long time, though I suppressed it or considered it just youthful imagination or wishes, but my gender identity is pretty androgynous. I go either way sometimes.
To actually answer the question, though, being transgender is definitely a cognitive thing, in my mind.
I just think more open-mindedness is needed about the trans community in the general population.