retrograde inversion

Several times in your life you may hear it noted that the retinal image is reversed and upside-down. Fewer times than that, hopefully, you may then hear it noted with curiosity that the brain somehow undoes this retrograde inversion. When you do hear this, please interject with the following:

"The brain does not reverse the coordinates of the retinal image. The brain does not know or care about about the retinal image's orientation relative to the world; as far as the brain is concerned, the image is not upside-down, or upside-up, or flipped or double-flipped. It is not delivered to the brain with reversed coordinates, but with no coordinates at all. The brain assigns spatial coordinates to the visual information it obtains from the eyes. It does this by integrating information about body position, gravity, and other consistent sensory cues about the state of the world. There is no reversal or correction of coordinates, there is only assignment of coordinates."

You will promptly be thanked for clearing up the misunderstanding, and hopefully your interjection will serve to end one strain of a particularly irritating bit of pernicious nonsense.

Thank you.