The Ostrich Problem

Maya's sister had gone to get pizza and left her laptop open, which was practically an invitation.

"It's a homework thing," Maya said. "She has to write about it. Look, it labels pictures."

Soren leaned in. On the screen was a photo of a school bus, and under it in green letters: school bus, ninety-eight percent.

"Okay," he said. "So it works."

"Try another one."

They dragged in a picture of a cat. Cat, ninety-six percent. A picture of a coffee mug. Coffee mug, ninety-four. Soren was already losing interest, which was usually the moment Maya found the thing worth being interested in.

"There's two folders," she said. "This one says bus. This one says bus underscore two."

She opened bus underscore two. It was the same school bus. Same yellow. Same little stop sign folded against the side.

"It's the same picture," Soren said.

"Drag it in."

He dragged it in.

Ostrich, the laptop said. Ninety-nine percent.

Soren laughed, the surprised kind. "It's broken. Your sister broke it."

"Put them side by side."

They opened both buses on the screen at once. Maya put her nose almost against the glass. Soren did too. Yellow bus. Yellow bus. Stop sign. Stop sign. Windows, wheels, the little black lettering they couldn't read.

"They're the same," he said. "Maya, they're actually the same. I'm looking at every part."

"They can't be the same. One's an ostrich."

"To it."

"To it," she agreed, and went quiet.

Soren reached into his bag and took out his notebook. He wrote: bus 98 percent. bus2 99 percent ostrich. same picture?? Then he held the notebook up next to the screen like it might help.

"What if it isn't the same," Maya said. "What if it's changed in a way we can't see."

"Changed how? I'm looking right at it."

"So are your eyes. But your eyes are, like, this much good." She held her finger and thumb a little apart. "Not infinity good."

Soren thought about that. "You mean there could be differences too small for us."

"Too small for us. Not too small for it."

He scrolled through the folder. There was a third file, a small text document. He opened it. Most of it was numbers, but at the top someone, probably her sister or her sister's professor, had typed a note.

max perturbation: one step of brightness per pixel. imperceptible to humans. adversarial. do not delete, needed for lab.

"One step of brightness," Soren read. "Per pixel."

"What's a step of brightness."

"The smallest amount a pixel can get brighter or darker. Like, the tiniest. You can't see one step. Nobody can see one step."

Maya sat back. "So somebody made every pixel a tiny bit brighter or darker. The smallest possible. In a pattern."

"A pattern we can't see, because each piece is too small." Soren was writing fast now. "But it added up to something the computer could see."

"Added up to a ghost of an ostrich." Maya grinned. "Painted onto the bus in a color we don't have eyes for."

They looked at the two buses again. Soren found he couldn't stop looking. Somewhere in that second picture was a whole other animal, laid over the yellow like the thinnest fog, and his eyes, his good, ordinary, this-much eyes, walked straight past it every single time.

"Try to find it," Maya said. "The difference. Try really hard."

Soren tried really hard. He looked at the top corner. He looked at the wheels. He looked until his eyes stung. "Nothing. It's a bus. I would swear on anything that it's a bus."

"You'd swear. And you'd be right. And it'd be an ostrich."

"We can't both be right."

"Why not." Maya turned to him. "You're seeing a bus. That's true. It's seeing an ostrich. That's true for it. The picture is holding both and we only get to see one of them."

Soren stopped writing.

"That's the part," he said slowly. "That's the weird part. It's not that the computer is worse than us. Everyone thinks it's worse. It saw something that's genuinely there. We're the ones missing it."

"We're missing it right now," Maya said. "It's on the screen. It's between us and the screen. And we can't."

They were both quiet then "Do you think," Soren started.

"Yes," said Maya.

"You don't know what I'm going to say."

"You're going to say, do you think there's stuff like this everywhere. Little patterns too small or too something for us. In everything we look at."

Soren closed his mouth. "Yeah," he said. "That's what I was going to say."

"Then yes."

He wrote one more line. Every picture we've ever seen. Then he put the pen down because his hand wanted to keep going and he didn't have the next word yet.

"Let's make one," Maya said suddenly. "Not to break it. To see. Take the cat. Feed it back in with the bus's ghost on it. See what it thinks."

"We don't know how they made the pattern."

"Then we drag the cat in a hundred times and change one tiny thing and watch when it flips. We hunt for the edge."

Soren looked at her. "That could take all night."

"Pizza's twenty minutes away."

He dragged the cat in. Cat, ninety-six percent. Maya reached over and nudged the brightness one notch, the smallest notch the slider had, so small the cat did not change at all to either of them, not one whisker.

They dragged it in again.

The two of them leaned toward the glass, shoulders touching, watching the green letters, waiting to see what the machine would say the cat was this time.