Thanks to Dr. Dan Press for a fascinating video he shot of his son (and our grandson) Ethan showing the concept of mirror invariance advanced by Stanislas Dehaene. You may vaguely recall the name Dehaene, about whom we blogged in December 2010.
Dr. Dan found a wonderful article by Dehaene written for Cerebrum titled Inside the Letter Box: How Literacy Transforms the Human Brain. Here’s what Dehaene wrote about mirror invariance, as related to reading acquisition, as demonstrated in the video below:
Early on during reading acquisition, most children generalize across mirror images to such an extent that they are able to read and write their first words independent of orientation. Just ask any 5- or 6-year-old child to write his or her name next to a dot located near the right side of the page. Most of them will unhesitatingly solve the problem by writing from right to left. This mirror competence slowly disappears during reading acquisition, but it remains present in illiterate people who, contrary to literates, exhibit no cost at all in recognizing a learned object in mirrored form. Indeed, illiterate people find it extraordinarily hard not to see “b” and “d” as identical shapes. The breaking of this spontaneous mirror invariance is one of the important outcomes of literacy.
So here we go, with Dan doing the Dehaene experiment on Ethan, who just turned 5 years old (that’s little sister Eva being vocal in the background):
As you can see, when Daddy prompts him to write his name next to the dot on the right, Ethan performs a perfect mirror sequence of the capital letters. When he then directs him to write his name next to the dot on the left, the mirror effect is gone. Ethan is just at the beginning phase of learning to read, and we anticipate that as he does (as predicted by Dehaene’s research) the mirror effect will progressively diminish. This is a huge concept for developmental optometrists to be aware of in terms of the persistence of mirror writing – even in the form of reversals – as related to reading acquisition.
If you’d like to read further about the topic, here is a nice article from Frontiers in Psychology that is part of a research series on the impact of learning to read on visual processing.