One example that is very clear in my mind is from Mark Twain’s The Tragedy of Pudd'nhead Wilson. In one particular scene, the title character is walking down the street when he hears a female voice speaking loudly from behind him in the distinctive dialect of a black slave. He turns around, expecting to see a black-skinned woman, but instead sees a fair-skinned woman. The woman’s name is Roxy and she is a slave, despite her white skin; “To all intents and purposes Roxy was as white as anybody, but the one sixteenth of her which was black outvoted the other fifteen parts and made her a negro. She was a slave, and salable as such. Her child was thirty-one parts white, and he, too, was a slave, and by a fiction of law and custom a negro”. The point Twain is trying to make, and I think that Gates would agree with it, is that Roxy speaks in such a way because that is how she was brought up to speak, to think that she had to speak that way as a genetic pre-disposition, despite not having any other physical traits. It is also worth noting that the major plot point of the story is that Roxy switches her child with that of her master’s. The both of them were both so fair-skinned, that the only way to tell them apart was their clothing. Roxy’s child grows up being taught to speak the “white” way, while the master’s child, now under Roxy’s care, was brought up to speak in the slave dialect. Obviously, their genes did not enable them to speak the “proper” dialect connected to their race. They spoke as they were taught to.
By entertaining preconceived notions of how a specific race should sound, we really learn nothing at all about the person who is actually speaking.