If you have an unreasonable fear of escalators, there may be something to it—but the problem involves looking at one, not stepping on it. Researchers report in the journal Current Biology that just looking at the rigid, geometric pattern of stripes—even still images of them—affects our brain in a way that in extreme cases can produce seizures and migraines.

Objects as seemingly innocuous as radiator grills "can be provocative," one expert tells the Telegraph, and patients with pattern-sensitive epilepsy have to cover them as a preventive measure.

"Vertical orientation of stripes are in general worse than horizontal," says one researcher. "Examples of striped patterns that are potentially provocative in daily life are rolling stairs, venetian blinds, striped clothes, and buildings." While the exact reason why is still a mystery, scientists say that stripe patterns increase our brains' gamma oscillations, which are linked to both headaches and seizures.

One hypothesis is that because the "extreme regularity" of things like blinds and escalators does not exist in nature—even the stripes of zebras aren't perfectly patterned—our brains have not evolved to cope with them, reports the Guardian.

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As researchers blurred the edges of lines or distorted them slightly, those oscillations reduced. They issued a warning with their findings, but added that "even perfectly healthy people may feel modest discomfort from the images that are most likely to trigger seizures in photosensitive epilepsy." Next the team hopes to develop a model to predict which images are most likely to provoke these episodes.

(Dozens of people tried to induce a seizure in this reporter.)

This article originally appeared on Newser: Our Brains Haven't Evolved to Handle Stripes