In the 1990s, Nancy Kanwisher was in an fMRI  machine recording responses from her own brain.

Weird hobby, I know. But when she looked at images of people's faces, she noticed something  peculiar about her responses.

A small part of her brain was  way more active than the others. As it turned out, she had stumbled  upon a new part of the brain. Today it’s called the fusiform face area:   an entire region partly  dedicated to recognizing faces.

The discovery revolutionized  this area of neuroscience, and led to some other pretty amazing findings. Like the fact that blind people use this  area of the brain to identify faces, too. And that sometimes, all you need to  recognize a face is the sound of chewing. [♪ INTRO] This episode was made in  partnership with the Kavli Prize.

The Kavli Prize honors scientists  for breakthroughs in astrophysics,   nanoscience and neuroscience, transforming our understanding of  the big, the small and the complex. There’s a long, sometimes  proud, sometimes regrettable,   history of scientists experimenting on themselves. It’s happened enough times to fill  multiple SciShow videos with examples.

I’m not saying it’s the recommended protocol, but  there’s something kind of cool about a scientist   who’s so confident in the safety of their  methods that they become their own test subject. And Kanwisher is certainly part of that history. In her case, she studied her own brain.

Let me transport you back in time to the late 90s. Seinfeld was reinventing the sitcom. The Cold War was finally over.

And Smash Mouth was popular for some reason. Things were changing in neuroscience, too. Scientists were finally getting to use tools like   functional magnetic resonance  imaging, or fMRI, machines that let them see inside the  brain while it was still working.

At the time, there were only  four fMRI machines in the world. So if you had a chance to use  one between the hours of 6 and   9 AM on a Saturday morning, you jumped at it. And if the experiments you were  able to run at that unpopular   time of the week didn’t yield significant results… Well, you didn’t get out of bed for nothing.

You’re going in that machine! Or at least Kanwisher did. At first, she wanted to study if our mind’s eye  uses the same neural pathways as our actual eyes.

She wondered at what point in  the process attention butts in, and how we reconcile new information  with what we’ve seen in the past. But after those investigations didn’t pan out, Kanwisher figured her best shot at getting  some publishable data was to look at faces. Neuroscientists knew that humans and other  animals have brain cells that respond to faces, so that was at least a starting point.

But they didn’t know much else about the process. When Kanwisher got in the fMRI machine  and looked at pictures of faces, she noticed that one part of her brain  really stood out from the others. It was way more actively involved in  facial processing than any other part.

She knew she was onto something. So her research group compared several other  people’s brains and found that, in many cases, this region of their brains was  particularly excited by faces, too. The fMRI images showed much less activity  in that area of the brain when her study   participants looked at pictures of  houses, hands, crabs, or other objects.

It appeared to be attuned to faces. And that includes the faces  of other animals or cartoons. So that explains why they decided to include  “face” in the name of this region of the brain.

And since it happened to be located in a  part called the “fusiform gyrus,” presto! We had the fusiform face area, or FFA. Kanwisher’s team wouldn’t have discovered the FFA  without the data from people in fMRI machines.

But those techniques couldn’t tell  them what was going on inside the FFA, like which brain cells were responsible  for focusing on each minute facial detail. For that information, one of her  postdoctoral researchers, Winrich Freiwald, and a collaborator, Doris Tsao, turned to monkeys. The monkey version of the  FFA is not identical to ours,   but it’s similar in its selectivity for faces.

In fact, these researchers published a   whole monkey/human comparison  showing how similar they are. So they put monkeys through the fMRI machine just  like Kanwisher and the other human participants. The monkeys were shown the same kinds  of images that the humans had been, and the researchers recorded responses of  individual cells within the monkey FFA.

They found that more than 90% of them  were dedicated to facial recognition. Now that they knew that most cells in the monkey   FFA worked together on the same  project of recognizing a face, this research team took their  findings to the next level. They successfully predicted which face the monkey  was looking at based on which cells were active!

It’s like looking at a quadratic equation   and knowing what shape will appear on  the resulting graph, but for brains! Like, literal mind reading! As you’ve probably guessed, monkey mind-reading  wasn’t necessarily the end goal of these studies.

People are pretty self-centered. So we still had a lot to learn about how  human FFAs work under different circumstances. Like when you can’t see faces at all.

Which led to the next study. The most surprising thing about  the FFA might not be how specific   it gets, but how broadly it’s used. I mean, you could be born blind and still have   an active FFA used for the same  purposes as a sighted person’s.

This was another big Kanwisher study. One of the first challenges her team faced was  designing an experiment for people who can’t see. They got around that in a few ways.

One of them was 3D-printing models  of faces, hands, chairs, and mazes for blind people to touch while  they were in an fMRI machine. They tested sighted people to see how their brains  responded to touching a face versus seeing one. In both cases, the FFA was activated.

Then, they compared the results of blind  participants touching those models with   sighted participants doing the same, and they  found their results lined up really nicely. And to add another layer of assurance,   they swapped out the feeling of  a face for the sounds of a face. They compared laughing and chewing with other  sounds like walking, clapping, engines, and waves.

And the laughing and chewing  sounds that come from faces   activated the participants’ FFAs  more than any other sounds tested. Whether it’s through touch or sound,   they showed that you don’t need  to see a face to recognize one. In fact, the FFA works the same  way for people who have never   seen a thing in their lives and people  who look at stuff all day every day.

Maybe because it’s connected to the same other  parts of the brain that help fill in the blanks. Which might explain why there are people  who can see but still don’t recognize faces. It’s a condition called prosopagnosia.

In those cases, the FFA seems  to work just like anyone else’s. But its communication with other  parts of the brain may go haywire. Thanks to our understanding of the  role FFA plays in facial recognition, we’re getting closer to figuring out what’s  going on with that condition and others like it.

So just like we needed multiple researchers  to come together to make these discoveries, we need many parts of the  brain to work together to   create our view of the world and the people in it. For their contributions to our understanding  of facial recognition, Kanwisher, Freiwald,   and Tsao were awarded the  2024 Neuroscience Kavli Prize. You can learn more about their research and  personal journeys at www.kavliprize.org. [♪ OUTRO]