
Stepping Feet Illusion - Reedx
https://en.wikipedia.org/wiki/Stepping_Feet_Illusion
======
gnagatomo
Had to do a basic CSS implementation to see how it looks in 60fps
[https://jsbin.com/ledomilaso/edit?output](https://jsbin.com/ledomilaso/edit?output)

~~~
twelfthnight
Is it just me, or does the illusion change a little? Instead of the step, it
almost seems like the yellow and blue rectangles are expanding and contracting
at alternating times. (hmm, only when I don't focus on the rectangles, but
somewhere else on the page)

~~~
cakoose
I noticed that too. I think it's because the buses are 3 stripes long instead
of 4.

After I changed the "\--bus" CSS variable from 30px to 40px, I got the
stepping effect.

~~~
ehsankia
That's really fascinating. Multiples of 20 give the stepping effect, while the
other offsets of 10 grow and shrink. Stuff in between do a strange shrink and
stop and grow. I thought 20 looked the best though.

I always loved making web remakes of common GIF illusions [0] where you can
mess with variables and see what impact it has. This is a perfect example of
that.

[0] [https://ehsankia.com/cjs/#19](https://ehsankia.com/cjs/#19)

~~~
equanimitivity
This makes some sense: to maximize the illusion, both leading and tailing
edges of the bus should be going through the light and dark strips at the same
time.

------
djmips
If you want to play with it you can interactively with some javascript here.
Holding the mouse down removes the vertical striping. You can also edit the
code.

[https://www.khanacademy.org/computer-
programming/illusion/45...](https://www.khanacademy.org/computer-
programming/illusion/4542031283617792)

------
eindiran
Very cool illusion.

If I unfocus my eyes and look at only one of the buses, I can see that it is
moving at a constant rate across the stripes. But the moment I try to look at
both, the illusion takes over. I can sort of get half the illusion by focusing
my attention on one of the buses, but still 'noticing' the movement of the
other: in that case I will see the bus I am paying attention to move at a
constant rate and the other bus move in a stepping motion.

~~~
lovehashbrowns
When I focused my eyes somewhere away from the screen and I tried to observe
the buses from my peripheral vision, I saw them move together at the same
time. But at some point my brain caught up and they did the stepping thing
again, even in my peripheral. Such an interesting illusion!

------
corey_moncure
To me, the colored rectangles appear to be moving at the same speed, but with
an alternating intermittent forward motion. The yellow rectangle will jerk
forward, then the blue, then the yellow, and so on across the field.

~~~
golem14
Hence the name “stepping feet”

------
gauravphoenix
>This special illusion shows how the background of the object or the object
around it has a significant effect on the perceived speed of the object

Does it imply that if I drive a brighter color car, it will appear that I am
driving faster? (when compared to a darker color car traveling at the same
speed)

~~~
wruza
I think that this illusion is based on low-contrast change when brighter bus
moves in to a brighter stripe (and vice versa). Your eye can’t tell yellow
from white as much as it can tell blue from white. If you’re driving on a non-
striped road that doesn’t work.

But I’ve read that if you look at a darker car moving _at_ you, you’ll
perceive it is a little less threat than e.g. red or neon-colored one, because
dark contours “grow” slower. (Similar thing, but can also be a stereotype bs,
learned lots of these before debunking via internet era came)

------
fyp
The reference links are also pretty cool: [https://michaelbach.de/ot/mot-
pigeonNeck/index.html](https://michaelbach.de/ot/mot-pigeonNeck/index.html)

------
wruza
(Don’t) see also:
[https://en.wikipedia.org/wiki/McCollough_effect](https://en.wikipedia.org/wiki/McCollough_effect)

 _McCollough originally reported that these aftereffects may last for an hour
or more.[1] However, Jones and Holding (1975) found that 15 minutes of
induction, when time-elapse testing is employed, can lead to an effect lasting
up to 2.8 months.[2]_

------
jmole
wish they had a GIF with higher framerate. I'm on a 120Hz monitor and wonder
how pronounced the effect would be with smoother motion.

~~~
Reedx
Here's a high quality version:
[https://www.youtube.com/watch?v=wAMN1QW5ByM](https://www.youtube.com/watch?v=wAMN1QW5ByM)

Also shows what it looks like in pure black & white at the end.

~~~
bmcooley
Interesting, I had a much easier time seeing the actual motion instead of the
illusion in black and white over colored.

------
rsiqueira
The stepping illusion was created today using just 140 characters of
JavaScript, see the illusion animation here with interactive source code:
[https://www.dwitter.net/d/17527](https://www.dwitter.net/d/17527)

------
pianoben
This feels related to "The Dress", somehow (is it blue and black, or white and
gold?).

Do these separate illusions share a common cause (high/low contrast colors
juxtaposed)?

