If stripes never go out of fashion, they are never as trendy as at the end of a long winter, when at the dawn of a finally sunny day, the temptation to dress like a 19th century French sailore century becomes irresistible. Last spring, not only did stripes make a comeback (I swear Gap’s green striped ensemble was following me all over the windows), but they made a splash in the high fashion world.
“At the spring 2025 shows, we saw stripes at Prada, Proenza Schouler, Louis Vuitton, Chanel, Dior, in practically all the collections present on the catwalks”wrote journalist Jaclyn Alexandra Cohen in the American fashion magazine Harper’s Bazaar last April. And not just any stripes: the stylists chose boldness, luminosity and a little touch of madness. They even layered stripes on top of other stripes (as seen in the video below).
This trend clashes head-on with popular wisdom which states that it is best to avoid stripes, specifically horizontal stripes which, like a fairground mirror, are supposed to make you appear wider than you really are. If everyone knows that horizontal stripes are not figure-flattering, then why are they everywhere?
The art of optical illusion
It’s not that we’ve abandoned our cultural obsession with thinness (really not, if only!). Perhaps this is due, at least in part, to the fact that slimming enthusiasts have the wrong idea about stripes. It is true that they modify our perception of the size of objects and bodies. But the effect occurs in the opposite direction: horizontal stripes make you look slimmer. It’s the vertical stripes that get bigger.
This is explained by two optical illusions. First of all, the Helmholtz illusion, which consists of two squares each with seven lines. In one of the squares, the lines are stacked (so seven horizontal lines); in the other, they are aligned (seven vertical lines). The squares have strictly the same dimensions, but the one that includes the horizontal lines appears narrower and taller than the other. This is what it looks like (below, left).
This phenomenon is likely due to another illusion called the Oppel-Kundt illusion (above, right), which demonstrates that more filled space appears larger than the same empty space. Think about how a room full of furniture seems larger than an empty room. When the square is filled from top to bottom (the horizontal lines), it appears larger in that direction; that is, higher and narrower. As if your brain is telling you: “Wow, this space manages to fit all these lines stacked on top of each other, it’s super big!” When the same space is filled from side to side (the vertical lines), it appears wider than it is tall.
For reasons I don’t understand, but which I wildly admire, a small group of scientists set out to find out whether these illusions applied to striped clothing. In 2007, Japanese researchers suggested that the Helmholtz illusion might only apply to two-dimensional (2D) silhouettes. They argued that vertical lines on a three-dimensional (3D) object created a sense of depth, which would have a slimming effect and could override the Helmholtz illusion.
Contradictions and biases of judgment
But in 2011, as part of a study published in the journal i-Perception, two British psychologists from the University of York asked participants to look at models wearing both styles of stripes, before indicating which one seemed wider to them. It was the vertical striped models who won the prize. For the model wearing the horizontal stripes to appear identical to the other, it had to be 10.7% wider. “No evidence supports the widely held view that horizontal stripes magnify the human figure. All the evidence here points to the contrary.”the scientists concluded.
Some reservations, however. To begin with, the effect may vary. Another Japanese study from 2013 shows that the Helmholtz illusion is stronger on a thin person and that when the guinea pig thickens, it can be completely canceled (or even reversed). Furthermore, it is interesting to note that a misconception can fuel an error of perception.
Carried out by American researcher Jessica Ridgway, a 2015 study revealed that 77% of participants found that people wearing horizontal stripes looked wider than those wearing vertical stripes, the opposite of previous results. Some of them were then asked about their opinions on the subject and the majority explained that they had been taught that stripes were unflattering.
“I was always told that vertical stripes are thinner, while horizontal ones are not.”said a participant. Perhaps, says the author of the study, these people’s preconceived ideas influenced the way they perceived the stripes. Indeed, research shows that our beliefs literally change the way we see the world.
Of course, everyone should wear what they like. But if you avoided horizontal stripes like the plague or whole milk (again, it’s how you feel), really, you can revise your judgment.
