The Circles Don't Move | Hacker News Reader

The Circles Don't Move

twitter.com

98 pointsjeremylevy45 comments

There is a line on the inside and outside of the circles where the colors go in and out of sync with the circle as the arrows change directions - it snaps between trailing by half the length of the color segments, going being ahead by the same amount, or in sync.

When the outer edge of a part of the circle is trailing and the inner edge is ahead, the circle appears to move outwards; reverse this and it appears to move inwards. The parts where the circle appears to be moving up/down/left/right have one side set to the 'outwards' motion, the opposite side set to the 'inwards' motion, and the other sides in sync.

The human visual cortex has so, so many edge cases like this. It's wonderful!

what I found fascinating is that the effect is maintained even when you're not focused (like lens focus, not attention focus) on the circles. If you let your eyes relax their focus to a point beyond the screen, the blurry circles maintain the illusion.

And bonus points if you find the focal point where a third circle is in the middle which is a composite of both the left and right circles, and... it doesn't move. I don't know how to better explain the effects of letting your eyes wander out of focus and the artifacts it creates in your vision, but I'm sure someone will get it.

Took me a while to get an overlapping 3rd circle.

Feels almost normal on the left/right moving ones, but when the grow/shrink stage comes my brain has no idea what to do with the arrows. The arrows looked like they were both pointing in and out, sometimes flipping between them really fast.

Somehow the right side is slightly out of focus, but the left is sharp. I think I had each eye at a different focal point. Is that possible? lol

It sure is. It’s also quite interesting that i have to get very close to the screen to create that third circle, but then can get quite far without loosing it, even when looking at the right or left circle.

Yeah, my first guess is the movement of that faint inner line triggers the Parasol cells or some other movement detection cells in our retina (https://en.wikipedia.org/wiki/Parasol_cell).

Possible underlying circuit: https://www.cell.com/neuron/pdf/S0896-627318%2930105-3.pdf

This makes much more sense. I thought that my brain was unconsciously interpreting the meaning of the arrows, which was completely unbelievable to me.

I was thinking the same, covered the arrow with my thumb... didn't help at all.

This shows the circles without the inner circles: https://twitter.com/i/status/1331542934056001536

And this with stabilized rotation: https://twitter.com/spacecatmeowart/status/13316956817451499...

Super cool effect! This is the type of magic trick that becomes cooler as you learn more about it.

More than you wanted to know about the Reversed Phi illusion:

https://en.wikipedia.org/wiki/Phi_phenomenon

https://jov.arvojournals.org/article.aspx?articleid=2121864

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6661801/

It seems it may also leverage the "perpetual diamond" illusion that made the rounds last year, which mostly has to do with gradients on edges: https://journals.sagepub.com/doi/full/10.1177/20416695188157...

This needs a memetic hazard warning! I had just eaten, and the linked illusion caused me instant nausea/motion sickness, which has not gone away after hiding the browser tab.

Thanks!

I've just eaten too, so I won't look.

‘emetic’, surely? Although I am sure it will spread well on social media too.

A bit disappointed that the arrows are not what is driving this (see other comments).

But would it be possible to have a "semantic optical illussion"? Was any such thing discovered?

I thought it might be the arrows creating the illusion, so I covered them with my thumbs and it still worked.

Something like the lines with different arrows? If not, please refrain for inventing cognitive hazards until 2021, please.

https://gpuzzles.com/optical-illusion/length-of-lines/

It's possible to suggest a direction for the spinning dancer illusion.[1]

I don't have an example for you that actually has cues included, but you can do it with some success in your own mind. Decide you want to see it spinning clockwise, then look at it. Now look away, and tell yourself it's going to be spinning anti-clockwise, then look at it again.

I now that's not quite what you wanted, but I imagine you could achieve a similar result by showing a clockwise/anticlockwise cue on the image itself.

[1] https://en.wikipedia.org/wiki/File:Spinning_Dancer.gif

Either the compression is changing the circles a bit, or they do in fact move - I’ve held a piece of paper covering all but a slight edge of a circle (obscuring everything else) and I can see the edge expanding/moving ever so slightly.

Still not enough to call BS on the illusion, but it might actually help “augment” it a bit.

This needs a SCP number.

I’d love to see a version of this illusion with less compression. Does anyone have a higher quality link?

Part of what you think are compression artifacts-- the thin layer of "wrong" pixels-- are actually key to the illusion. That being said, yes there are still some compression issues.

Another copy here: https://gfycat.com/enchantedclearcutblackfish

I love how the compression artifacts are acting like a magician's sleight of hand, obscuring the changes to the border of the circle that create the illusion.

> Part of what you think are compression artifacts

I know what are compression artefacts and what is part of the illusion, no need to explain that to me. I just wanted to see the less compressed version.

It's a nice effect and others might find your comment useful, I just wanted to say that there was no reason to address your explanation to me.

https://twitter.com/jagarikin/status/1331409504953540613

This one was link to by a MIT Media lab guy

If you like optical illusions, I recommend visiting http://illusionoftheyear.com/ when you have some spare time.

Look at it from the side angle, and the circles don't move!

This is fake. Cover both the arrows and you’ll still see them move in the exact direction that the arrow suggests when you uncover it.

The movement is of 1px at best but it’s there.

You downvoted me, why don’t you try for yourself? Keep them covered for a minute so you’re sure that your brain isn’t messing with you, then look again and you’ll see it.

You are 100% right, this is fake and garbage. The circles DO move.

Actually, I lied, they don't move... checked again

The thing is, you are not wrong. It is fake. It's an illusion!

And very true, covering the arrow does nothing to prevent the illusion.

Nope. See the version with the lines. https://twitter.com/Jakesaurius/status/1331543133910396929

The illusion has nothing to do with the arrows, but the circles still don't move.

Huh? The circles move just a few pixels that are hidden by the thickness of the lines, but they definitely move.

I covered up the arrows and the effect lingered. That blew my mind.

Theres a very faint outline around the circles that controls perceived motion. If you pause the vid it becomes noticeable...

Me too, and I'm pretty sure they actually do move. When I place something on my screen covering the arrows, I can see circles moving (since the shape of the gap between covering and edge of circle changes).

EDIT: Or at least something in the edge changes.

The edge gets darker.

Id consider that to be a subpixel movement

If you lay a straightedge along the top of the circles, they do not remain aligned. It seems that the circles do move

You can use another window as a straightedge. :)

Yeah anything straight, really

I got downvoted for pointing out the circles actually move? Weird.

They don't, that's the whole point. Check it again - they only seem to move.

I disagree.

The border pixel is changing between three non-background colors. I would define that as moving.

https://twitter.com/Jakesaurius/status/1331543133910396929

The circles do not move. The outer most layer of pixels however, changes color, giving the illusion that they're moving.

Once you understand how the "outer-rim of pixels" contributes to the illusion, it all makes sense.

I consider a loss of a pixel on one side simultaneous with the addition of a pixel on the other side as "moving". Loss and addition here meaning "change in color"

Reply on news.ycombinator.com