These are all, as the IT people say, known issues. For a few minutes or an hour, long enough to play a game or watch a movie, they're minor annoyances. But wear perception-shifting glasses for days at a time — as Bailenson's team of researchers did — and the problems get worse. Way worse.The reviews are in, and the tech press is lauding the Apple Vision Pro headset for delivering on the company's promises. It's well-designed, the video and sound are startlingly precise, the "Minority Report"-style gestural interface is future-tastic. Nobody's exactly sure what it's for, or whether even the Readiest Players One will spend $3,500 on it, but hey — that's gadgets for you.

Still, this is a new gadget frontier. The Vision Pro, like the similarly kitted-out Quest 3 and Quest Pro headsets from Meta, uses what's known as "passthrough" video — cameras and other sensors that capture imagery of the outside world and reproduce it inside the device. They feed you a synthetic environment made to look like the real one, with Apple apps and other non-real elements floating in front of it. Apple and Meta are hoping that this virtual world will be so compelling that you won't just visit. They're hoping you'll live there.

That, unfortunately, could have some very weird and very messy consequences for the human brain. Researchers have found that widespread, long-term immersion in VR headsets could literally change the way we perceive the world — and each other. "We now have companies who are advocating that you spend many hours each day in them," says Jeremy Bailenson, director of the Virtual Human Interaction Lab at Stanford. "You've got many, many people, and they're wearing it for many, many hours. And everything magnifies at scale."

Meaning: Our brains are about to undergo a massive, society-wide experiment that could rewire our sense of the world around us, and make it even harder to agree on what constitutes reality.

The short-term side effects of virtual reality are well established. People in synthetic environments tend to misjudge distance, both at a distance and close up. That's no surprise: Even in the real, three-dimensional universe, our ability to determine how close or far away something is is subject to all kinds of external factors. Virtual environments, with their lower resolution and synthetic 3D, make all that worse — which is especially bad if you're one of those users posting videos of yourself doing things like skateboarding and driving while wearing a mixed-reality headset.

You think your hands are in one place, they're actually in another, and pretty soon you're driving your Honda Civic through a supermarket.

Objects in a headset can also get funhoused. That's called object distortion — things get warped, and change size or shape or color, especially when you move your head. A video render can't compete with the processing speed and fidelity of your eyes and brain.

These are all, as the IT people say, known issues. For a few minutes or an hour, long enough to play a game or watch a movie, they're minor annoyances. But wear perception-shifting glasses for days at a time — as Bailenson's team of researchers did — and the problems get worse. Way worse.

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