Ishihara, eat your heart out


Today’s xkcd seems to have been tailor-made to press all my geeky buttons at once. Take a close look, and see what you see. And when you’re done, read on to see what I see.


Here’s what my synesthesia tells me this looks like.¬†

Of course I do have¬†synesthesia, and I’m not colorblind. Bully for me! But the fact that I can actually see the pattern here is rather lucky: it just so happens that all of the numbers Randall chose to include in the foreground have warm colors, and most of the others are cool, so the background literally recedes for me.

But wait. What’s that he said about colorblindness? The most common forms of colorblindness are protanopia and deuteranopia, where people are missing either the red or the green light-sensing cones. Both have trouble distinguishing reds from greens and browns. Which just happen to be the colors inside the numbers for me. And as you can see below (um, if you’re not colorblind, that is) the big numeral 4 contains red 2’s, and the big 2 contains brown 9’s. So if you actually used my synesthetic picture of this thing as a colorblindness test, it might actually kinda sorta work!

I’ve never met Randall Munroe, but I’m starting to wonder. Randall, if you’re reading this, fess up. Did you crib my colors?

The answer was right in front of us all along!

5 thoughts on “Ishihara, eat your heart out”

  1. But wait, it’s not that simple! Coincidentally, I was having a conversation about exactly this topic yesterday afternoon. Ramachandran has documented one case of a colour-blind synaesthete (see the relevant section at That person’s synaesthesia was unaffected by colour blindness, so that they would perceive colours through sensory mapping that they couldn’t see in the world. Presumably that person’s colour perception apparatus could be tickled at a deep level, even though their cones couldn’t generate an equivalent signal. So it’s not clear that you can design a test like Munroe’s to find colourblind synaesthetes. Man, I love this stuff.

  2. Didn’t you notice Randal Monroe at your birthday? Or maybe you couldn’t because he camouflaged himself against your hot pants pink livingroom decor, all done up in H’s and U’s!

  3. I’m a synesthete that sucks majorly at that kind of puzzle, haha. Though interestingly, my perception was quite the opposite of yours – the colours making up the numbers were (mainly) cool, and the background was warm. Looking back at it, I still can only really make out the ‘2’. 2s and 7s make up the ‘4’; 2 is yellow, so it blends into the warm background, and 7 is mostly colourless so I don’t pay it much attention.

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