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Doris Tsao / Caltech

Researchers believe they've cracked the code for how primates are able to recognize faces. And, it may be relatively simple: only 200 neurons or so in the brain appear to be responsible for the ability of macaque monkeys to identify the faces of humans that they know over those of complete strangers.

Why it matters: Humans and other primates are thought to use a similar face recognition system, so understanding how images are encoded by the neurons could inform the development of artificial vision.

The question: Researchers had previously identified six parts of the brain (in a place called the inferior temporal cortex) that were responsible for identifying faces. Specific nerve cells in these six regions of the brain respond more strongly when we see faces compared to objects. What scientists didn't know was the exact combination of these "face cells" required to identify those we know from strangers.

The study: Researchers inserted electrodes into the brains of macaque monkeys in the six regions. They then mapped various features of faces (like the distance between eyes) onto a grid and used them to create 2000 photos of manipulated human faces. When they were shown to the monkeys, just 205 neurons from two of the six regions where "face cells" exist activated. Using the pattern of neuron activation, the researchers were then able to reconstruct the faces the monkey was looking at.

Fun quote: "People always say a picture is worth a thousand words. But I like to say that a picture of a face is worth about 200 neurons." —Doris Tsao, professor of biology and biological engineering at the California Institute of Technology.

Go deeper

Kendall Baker, author of Sports
2 hours ago - Sports

2021 Tokyo Olympics hang in the balance

Illustration: Aïda Amer/Axios

10 months ago, the Tokyo Olympics were postponed. Now, less than six months ahead of their new start date, the dreaded word is being murmured: "canceled."

Driving the news: The Japanese government has privately concluded that the Games will have to be called off, The Times reports (subscription), citing an unnamed senior government source.

Biden's centrist words, liberal actions

Illustration: Sarah Grillo/Axios

President Biden talks like a soothing centrist. He promises to govern like a soothing centrist. But early moves show that he is keeping his promise to advance a liberal agenda.

Why it matters: Never before has a president done more by executive fiat in such a short period of time than Biden. And those specific actions, coupled with a push for a more progressive slate of regulators and advisers, look more like the Biden of the Democratic primary than the unity-and-restraint Biden of the general election.

3 hours ago - Technology

Review of Trump ban marks major turning point for Facebook

Photo Illustration: Aïda Amer/Axios. Photo: Saul Loeb/AFP via Getty Images

Facebook's decision to ask its new independent Oversight Board to review the company's indefinite suspension of former President Trump is likely to set a critical precedent for how the social media giant handles political speech from world leaders.

What they're saying: "I very much hope and can expect … that they will uphold our decision," Facebook's VP of global affairs Nick Clegg tells Axios.