
If you are born a male, people accept you as a boy and a man, and if you are born a female, people accept you as a girl and a woman. You may not be accepted by everyone as a "good example" or as an epitome of manhood or womanhood, nor as an attractive specimen of one, but generally, you are accepted as a man/woman simply based on your birth sex, regardless of your personality, appearance, and actions.
People perceive your gender based on their belief about your physical sex, which is mainly based on your physical appearance, but also on things such as your name and on what gender other people have ascribed to you. Perception and acceptance go hand in hand. If you are perceived to be male, you are accepted as a man, and if you are perceived to be female, you are accepted as a woman; at least, until those perceptions are brought into question. When someone is perceived as one sex, but then discovered to be another sex, people generally change their idea of that person from being a man or woman to vice-versa. This mental shift isn't something as simple as "Oh, I thought he had green eyes but they are actually blue"... it's a radical shift in perception of the person.
When a transsexual person has a sex-change, it is just a physical change; a change in appearance. Their personality remains basically the same. If they had been born their target sex instead of having had surgery and hormones to achieve it, they would have been accepted as that gender by general society. Yet, the fact that they had to change their body causes some people not to accept them as their stated gender. These people think there is something inherent in one's birth sex which makes one a man or woman, and that this cannot be changed even when the body is changed, or even when the person claims that their gender never matched their physical sex.
In this book I am reading, it sounds like the mother, when first coming to terms with her child being transsexual and having a sex-change operation, could not understand that her child was still the same person he had always been. To her, he had previously been a woman, and was now becoming a man, and to her, men and women are different, and so therefore he was becoming someone different than he had been before. This bothered her, because she felt she was losing the child she had known, when really the child was just going through a physical transformation.
People have subconscious preconceptions about what men are usually like and what women are usually like. Perhaps these preconceptions may change slightly over one's lifetime, influenced by the people one interacts with and the things one experiences. But once these subconscious preconceptions are formed in early childhood, they are the mental templates which the mind uses when thinking about actual people. The less well-known the actual person is, the more these templates are used to "fill in the missing picture" about that person in one's mind. As one interacts more with an actual person, that person may no longer fit cleanly within one's mental template for that gender, but that template still somehow affects how one thinks about the person.
Given two people, one who appears male and one who appears female, both with the exact some personality and mannerisms, I would still perceive them differently not just based on their appearance, but also on my mental gender templates. I am most definitely not immune to these kinds of preconceptions. And shifting the gender template I use for someone is not an easy task for me either. The more a transgendered person's physical appearance resembles their "target" sex/gender, the easier that mental shift is for me. This is why transgender people like being able to pass... it makes it easier for other people to perceive them as they perceive themselves.
Perhaps some of those gender preconceptions are valid... a man who is soft-spoken, kind and gentle probably would still have had a very different life than a woman who is soft-spoken, kind and gentle... but not necessarily.
It is hard to figure out what one's gender pre/conceptions are... they are like mental flavors, as I've written before. Not necessarily any kind of hard and fast beliefs about what a man must be like, or what a woman must be like, but... flavors... fuzzy fill-in-the-blank-nesses, and if there are no blanks, then surround-perception-of-person-with-this-flavor-ness.
And what is the correlation between perceived gender and sexual attraction? Why is it that I can feel sexual attraction to some people whom I perceive to be a "man" or a "non-woman", whereas I feel like I couldn't feel sexual attraction to a "woman"? Is my mental template for "woman" only composed of things I am not sexually attracted to?