And even those who can't tell by looking down almost always know anyway, because our brain isn't so retarded it needs physical proof to tell itself how to operate.

The boy that John Money mutilated, molested, and abused to try and prove gender wasn't real knew his entire life he was a boy despite being given a facsimile of a vagina as a baby and raised to think he was a girl. He knew enough that it caused lifelong problems even before he could formulate in his brain what he knew was wrong.