What: This optical illusion is an alternate example of the “Fraser spiral” or “concentric spiral” illusion. Named by British psychologist James Fraser in 1908 [1], and while it doesn’t have rounded “loops”, the visual noise creates similar lines, causing the same effect.

If you couldn’t tell already by the general vibes, this is an Akiyoshi Kitaoka recreation [2], although I’ve added the spin to enhance the effect, as well as the colors.

As a hat tip to a previously built illusion, this effect is not particularly dissimilar to the “spirals but not spirals” [3].

How To: If you’re looking at this illusion, and seeing or feeling a spiral, then you’re experiencing it, as there are only circles drawn here, with a lot of extra squares and background noise to help you along.

You can click into the settings and change the colors, and the circle/step counts, allowing you to find different breaking points. I’ve set it up initially as per the original illusion design, but I found that there are multiple different points with more spirals and fewer, larger diamonds and fewer, and different colors that trigger my brain to fully spiral, so to speak.

Explain It:

The visual distortion is produced by combining a regular line pattern, which in this case are the checkers, with the distortion provided by the black and white squares which alternate in colors as the rings deepen. As well as the background and movement which really stack it all on. [4]

Your peripheral vision is doing the rest of the work, it’s all too much to take in and process easily so your brain fills in the gaps and you’ve got a “spiral”. Akiyoshi is a master of utilizing these techniques in colorful and vibrant ways, and it shows in this illusion.

Cites and Extras:

• [1] Fraser Spiral A look at the untouched Fraser Spiral (I should probably build one of these as well)
• [2] Akiyoshi’s Page showing the effect labeled “Water spirals” alongside other beautiful illusions, and with trademark bright colors!
• [3] Spirals but not spirals Prior built illusion of mine, with a similar effect
• [4] Akiyoshi slowly breaking down the effect with diagrams and math!
• Fraser illusion without local cues?, a good paper on the fraser illusion, which again isn’t completely explored here, can really show you the base effect in isolation.

I've researched these optical illusions in my spare time but am clearly not any kind of expert and my explainations are pretty smooth brained, if you find something mis-cited, earlier examples, or general mistakes please new let me know via toymaker@toms.toys, be kind!