Unflipping the Letters

mirrored toy dinosaurs

Human brains are designed to function in a 3-dimensional world. Because real-world objects are the same no matter which way they are turned, our brains are wired to automatically recognize reversed or mirrored versions of the same object as being the same. Scientists call this “mirror generalization” or “mirror invariance.” It is a natural brain function that has been tested and observed in infants and children, as well as in many types of animals. 1

But reading is a 2-dimensional process and many languages — including English – are written with alphabets that include visually similar letters that are mirrored version of others (d/b, p/q).

letter b and d

How the Brain Changes for Reading

In order to learn to read, a person needs to develop the ability to distinguish these mirrored letters, and to suppress the function of the brain that sees them as the same. There is a fancy scientific term for this process: enantiomorphy (the ability to discriminate between mirror images that develops through reading acquisition). This does not happen naturally, but is tied to the process of learning to read.

This brain change, which is also called mirror interference, is somewhat complicated because the part of the brain that perceives and processes letters is in the same area of the visual cortex that perceives and processes real-world things, particularly things such as animals (which of course tend to move around a lot). When a person learns to read, neurons that have developed for 3-dimensional perception must be “recycled” to be used instead to process letters and words. (“neuronal recycling hypothesis“)

Of course, the reading person still needs to retain the ability to mirror-generalize for all the real world objects that are seen, so the letter-reading ability that preserves directional information is something that can be turned on and off. Scientific experiments show that people are slower to recognize mirrored versions of pictures of things right after they have been looking at mirrored letter pairs. 2 3

It takes time to develop both the skill of mirror-interference, and the ability to switch the mirror-generalizing system on and off. That is why it is very normal for young children to confuse the mirrored letters up to around age 7 or 8 — and of course, the letter confusion typically persists much longer for dyslexic children. 4

How Dyslexic Strengths Make Reading Harder

tangram puzzle

Once we understand this process, it is easy to see why dyslexic gifts can stand in the way of reading. When my son was a toddler, he was an absolute whiz at manipulating shapes. At age 2 he solved a tangram puzzle to form an assortment of loose shapes into a square in seconds, as soon as he had been given the random pieces of the unassembled puzzle. The label on the toy box said that meant he was a genius! His prowess with lego blocks and jigsaw puzzles over the next several years seemed to bear that out.

Except for the fact that he couldn’t learn to read.

moving letter

So my guess is that for dyslexic kids like my son — the ones who have very strong spatial skills early on – the mirror-generalization part of the brain develops particularly strong connections. These might be particularly difficult to override or suppress when the time comes to try to focus on the letter “b” without the brain also simultaneously registering the letter “d.”

And researchers have indeed confirmed that dyslexic children perform better on tests of their ability to recognize mirrored shapes. “Dyslexic children were the only group whose shape-based judgments were immune to mirror-image differences because they failed to automatize mirror discrimination during visual object processing.” 5

It’s not that they can’t see the difference between a b and a d — it is that their minds can’t see one without automatically seeing the other. (And that is why tricks to help with memory won’t work — it’s not a problem with memory, but of the way the brain naturally responds to the visual input). The child who experiences this confusion needs a way to stop his brain from flipping the letters.

Ron Davis wrote:

“When dyslexic people look at an alphabet letter and disorient, within a split second they see dozens of different views — from the top, the sides and the back of the letter.”

“The dyslexic person needs to learn the disorientation switch on and off. “

Davis & Braun, The Gift of Dyslexia (2010), pages 131, 133
clay letters p q b d
clay letters by Kim Willson-Rymer

So the research science shows that what Davis attributed to disorientation is actually a natural process that has to be overcome in conjunction with learning to read. Typically-developing readers learn to do this naturally, without thinking about it; but it is not so easy for dyslexic children.

Davis describes orientation counseling as a means to stabilize perceptions. The brain science tells us that the person must first develop a separate mirror-interference ability, and then must learn to automatically switch on the mirror interference when needed for reading.

When I led my son through the Davis Orientation sequence at age 11, it seemed like a miracle. His struggling stopped, and almost immediately he was able to read with ease. The Davis Facilitator who evaluated my son explained that the orientation process would provide a way for my son to control a switch in his brain to disable the ability to disorient — but I assumed the facilitator was speaking metaphorically. But it turns out that there actually is some sort of internal mental switch — and the Davis orientation tools seem to be an effective means of controlling it.


  1. Kolinsky Régine, Fernandes Tânia. A cultural side effect: learning to read interferes with identity processing of familiar objects. Frontiers in Psychology. Volume 5, page 1224, 2014.
  2. Grégoire Borst; Emmanuel Ahr, Margot Roell, Olivier Houdé. The cost of blocking the mirror generalization process in reading: evidence for the role of inhibitory control in discriminating letters with lateral mirror-image counterparts. Psychonomic Bulletin & Review. Volume 22, Issue 1, pp 228–234, 2015. .
  3. Perea, Manuel; Carmen Moret-Tatay, Victoria Panadero. Suppression of mirror generalization for reversible letters: Evidence from masked priming. Journal of Memory and Language. Volume 65, Issue 3, pages 237-246, 2011.
  4. Stanislas Dahaene, Kimihiro Nakamura, Antoinette Jobert, Chihiro Kuroki, Seiji Ogawa, Laurent Cohen. Why do children make mirror errors in reading? Neural correlates of mirror invariance in the visual word form area.. NeuroImage. Volulme 49, Issue 2, 2010.
  5. Fernandes, Tânia; Isabel Leite. Mirrors are hard to break: A critical review and behavioral evidence on mirror-image processing in developmental dyslexia. Journal of Experimental Child Psychology. Volume 159, Pages 66-82, 2017.