The trouble of zero

65.168 - 79.321 Regina Barber

And Yasmin says that this idea of a placeholder wasn't totally unique. The ancient Maya, for example, had a little shell symbol that they used in a similar way. But zero didn't really become a number on its own until around the 7th century.

79.921 - 107.458 Yasemin Saplakoglu

There were Indian mathematicians who came up with a couple of ways to use zero as a number. And they were the kind of first to figure out that zero could be a digit, just like the other numbers, like 1 and 2 and 3. After that, it kind of went out from India to the Arab world. And then, you know, in the 13th century, Fominachi actually picked up the idea during his travels in North Africa.

108.079 - 112.587 Yasemin Saplakoglu

And he brought it back to medieval Europe, you know, along with the base 10 number system.

113.008 - 118.378 Regina Barber

But in medieval Europe, not everyone was thrilled about this concept of zero.

118.358 - 138.789 Yasemin Saplakoglu

People had difficulty with accepting it. It was kind of scary. People were confused by it. Some thought of it as like the devil's number that challenged like really deeply held ideas. And, you know, because of the influence of the church, like philosophers and theologians associated nothing with like chaos and disorder.

229.362 - 242.334 Regina Barber

Okay, Yasmin, before we get into the complexity of zero, let's just start with the neuroscience of numbers in general. You've done some writing about this, like how our brains comprehend small numbers differently than large numbers. Can you tell us more about that?

242.714 - 266.402 Yasemin Saplakoglu

Right, so this is actually kind of cool. We have what are called number neurons in the brain. So there are neurons that are tuned to specific numbers. There are neurons that favor, for example, the number five, and there are other neurons that favor the number seven. And so on. So that means that for the neurons that favor the number five, they'll fire more.

266.663 - 278.725 Yasemin Saplakoglu

Like if it sees five items on a table, it'll fire more than if it sees four or six. It'll still fire for four and six, but less and then even less for three and seven.

279.025 - 284.634 Regina Barber

Yeah, so these neurons are specifically for that number. They really like that number.

284.654 - 303.784 Yasemin Saplakoglu

Yeah, it's kind of neat that we have all of these. And there's a lot of questions surrounding it still. We don't know if there are neurons that fire for 1,505. That seems like there would be a lot of neurons in the brain then for the various numbers. I'm sure there's some other kind of mechanism there.

510.412 - 530.817 Yasemin Saplakoglu

Yeah. So the first group, the one that looked at a bigger scale, found that the brain processes zero similarly to other numbers. Basically, it puts zero at the start of a mental number line, like it's before one. Excellent. It showed the numerical distance effect, which is what they were looking for.

531.017 - 555.828 Yasemin Saplakoglu

So their conclusion was there's no difference in the way that the brain sees zero than the other numbers. Zero in terms of both the digit zero and like zero objects. The second group also found that the brain puts zero before one on the mental number line, but they found subtle differences that still made zero special in the brain.

556.569 - 580.414 Yasemin Saplakoglu

So, for example, they found that more neurons had zero as their preferred number than other small numbers. That suggested to them that the brain might be representing, you know, this empty set with more neurons. accuracy than it does for other small quantities. But this was only true for quantity zero. For the digit zero, they did not find any difference.

580.434 - 585.748 Yasemin Saplakoglu

Like the brain saw the digit zero like it does the other digits, like one, two, three.

586.167 - 595.528 Regina Barber

So in as you're doing this reporting, do you find that these like these conclusions are complimentary? Do you think that they're like fighting each other? What do you think?