Bye-bye, feeds that showed everything and everyone we followed in an unending, chronologically ordered river. Hello, high-energy feeds that popped with must-clicks.

At around the same time, Facebook—whose News Feed has been driven by algorithms since 2009—hid the setting to switch back to “Most Recent.”

No big deal, you probably thought, if you thought about it at all. Except these opaque algorithms didn’t only maximize news of T. Swift’s latest album drops. They also maximized the reach of the incendiary—the attacks, the misinformation, the conspiracy theories. They pushed us further into our own hyperpolarized filter bubbles.

“There are bad people doing bad things on the internet—QAnon, white supremacists—it’s not that Facebook, YouTube and other social-media sites allow it on their platform. It’s that they amplify it,” says Hany Farid, a computer science professor at the University of California, Berkeley.