What kind of an optical illusion is this? A line on a pavement.

June 30, 2024 2:42 AM

Hi, I just took this photo of a line painted on a pavement with some tiles removed and put back not in order . I rotated the center line to be exactly horizontal, but it still looks not horizontal. I know there are different types and categories of optical illusions with explanations on why we don't see what we think we see . Do you know what type of an optical illusion is this? Thanks, Hanan Cohen
posted by hananc to Science & Nature (10 answers total)

Which line is supposed to be horizontal? There are no horizontal lines in that picture and no vertical ones as far as I can tell.
posted by mmoncur at 4:09 AM on June 30

I don't understand what you mean. What center line?
posted by Mournful Bagel Song at 4:23 AM on June 30

That's an impressive jigsaw puzzle they've made of that white line!

I can't answer the question, other than saying something handwavy about perspective, but did you mean to say you'd rotated the centre line to be exactly vertical? I can't find any horizontal lines, but holding a ruler up against the screen, it looks to me as if the right-hand edge of the white line runs straight up from bottom to top of the photo.
posted by ManyLeggedCreature at 4:25 AM on June 30 [1 favorite]

Response by poster: Oy! I meant VERTICAL. Here is a screenshot from Photoshop showing a vertical (!) line marked in the middle of the painted line that's on the pavement.
posted by hananc at 4:32 AM on June 30 [1 favorite]

Whoa, I never would have guessed that that line (well, the center of it since it's in perspective) was actually vertical.

I assume the skewed brick pattern is messing up what we see? I don't know the name of the illusion though.
posted by mmoncur at 4:39 AM on June 30

I think this would be a variant of the Hering illusion. Or maybe Orbison illusion. They do get proprietary about their lines. Maybe we just stay "straight line illusion" and call it a day.
posted by phunniemee at 4:48 AM on June 30 [1 favorite]

Best answer: It's a 'visual tilt effect'. The argle of the horizontal-ish lines in the block paving pattern change your perception of the orientation of the vertical line.
posted by pipeski at 4:50 AM on June 30 [9 favorites]

so cool. my mind can't unsee the tilt. plus I am compulsively trying to put the tiles back into their right places.
posted by EllaEm at 5:55 AM on June 30

Looks perfectly vertical to me.
posted by lhauser at 9:56 AM on June 30

Now that this has been resolved, is there a story about why the tiles were removed and not put back into their original places? Was this intentional? Is it art? Is someone really sloppy and lazy?
posted by Reverend John at 12:44 PM on June 30 [1 favorite]