If the title to this post makes sense, you have learned to override the brain's default processing of mirror images (that they're the same object) to distinguish between the letters "b" and "d". Learning to read altered your visual processing system. One side-effect is that it now takes you more time to correctly label mirror images or writing as being different views of the same thing.
As highlighted by our favorite psychology professor Daniel Willingham in his blog last month, a team of clever researchers used this penalty and three experimental groups (literate adults - who learned to read as children; illiterate adults; and, formerly-illiterate adults) to answer the question: is there a point in brain development where non-readers can never be taught to see the difference between "b" and "d"?
In short, the answer appears to be no.
By showing the participants pairs of images consisting of identical, completely different, or mirror-reversed images, the experimenters showed that illiterate adults identify the mirrored-ones as rapidly as the identical ones. However, the literate adults and ex-illiterate adults take longer to correctly label these reverses as the same (much longer, in cases where the images are strings). In other words, learning to read modified the visual processing systems of the adults as it does in children.
Careful readers of NCTQ's work know that we care deeply about reading research (see page 13 of our Early Reading Standard Book, for examples) and that we frequently highlight Willingham's work.
It's a happy Friday when we can do both.