< The "shocking" tactic electric fish use to collectively sense the world

EMILY KWONG, BYLINE: You're listening to SHORT WAVE...

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KWONG: ...From NPR.

REGINA BARBER, HOST:

Hey, SHORT WAVErs, Regina Barber here. And this time, I've got two of our favorites for our regular roundup of science news. Ailsa Chang.

AILSA CHANG, BYLINE: Hi. Thanks for letting me hang out again.

BARBER: Always, anytime. And Anil Oza. Hey, Anil.

ANIL OZA, BYLINE: Hi, Gina. Always a pleasure to be here.

BARBER: Thank you, thank you. It is always a pleasure to have you. And as always, we're going to share three science stories in the news that have caught our attention recently.

CHANG: And I hear one of the stories is about a new satellite that tracks climate warming emissions from the oil and gas industry.

BARBER: Yep. And another one is about a sense of rhythm that shared among cultures all over the world.

OZA: And one story about a fish that uses electricity to communicate in groups.

BARBER: All that on this episode of SHORT WAVE, the science podcast from NPR.

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BARBER: All right, Ailsa, as our guest, which topic do you want to start with? What calls to you the most?

CHANG: Well, I'm kind of into all of them.

BARBER: Thank you.

CHANG: But I really, really have a bias towards little fishies.

OZA: Sure. So the other day, I took a trip up to a lab over at Columbia University. It's these funky looking fish. They're called elephantnose fish 'cause they have these long noses and elongated bodies.

CHANG: Oh, how cute.

OZA: I know. The researchers had this whole wall of them where they were separated in big, dark tanks, and I was kind of struggling to see them. But these fish have no problem with it because they actually use electricity to sense the environment around them.

CHANG: Whoa. So we're talking, like, electric fish, but they don't shock themselves, right?

BARBER: Well, I mean, these fish can send out weak electric signals from their tails, and they can pick up these electric signals from these sensors all over their body.

OZA: And to answer your question, Ailsa, these signals are weak enough that they don't shock each other or other animals. One of the researchers in the lab actually told me he'll sometimes stick his finger in the tank and play with these fish.

CHANG: This is not the same as sticking your finger in a socket, I trust.

BARBER: I hope not.

OZA: No. And while I was there, he stuck this electric sensor in the tank, too, to get an idea of all of that electrical activity going on. Here's what that sensor was picking up.

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CHANG: Oh, my God. It...

BARBER: Yeah.

CHANG: ...Sounds like staticky socks out of the laundry. So do we know why they do this?

OZA: Yeah. These fish come from Africa, where they live in really murky rivers where it's tough to see very far. So by putting out these electrical signals and seeing what they bump up against, these fish can much more easily navigate around this really cloudy water. Think of it like echolocation, but with electricity.

BARBER: And these researchers at Columbia University have now discovered that these fish can team up and combine their electric fields to sense a much wider area than they could alone. And they wrote about it this week in the journal Nature.

CHANG: That is so cool. So they're, like, coordinating. But how? Like, how do these fish all network together like that?

BARBER: Yeah. So imagine each of these fish is sending out an electric field around them. And if they swim near each other in a group, they create one huge electric field and they can tap into this. And once a predator or something enters that field, the fish will know instantly.

OZA: Yeah. And the researchers told me that these fish's brains are organized completely differently from our human brains. And this weird brain architecture might help the fish interpret this huge storm of electrical signals coming in.

CHANG: OK. So next up, you say we've got a story about rhythm from around the world.

BARBER: Yeah. So, Ailsa, it turns out that we all have rhythm, but not all the same rhythm.

CHANG: Oh, yeah. I see that on the dance floor all the time.

BARBER: Yeah. So I'm going to do a little audio experiment with you, Ailsa. I want you to listen to this, and I want you to try to match the beat pattern by clapping once you've heard it.

CHANG: OK.

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CHANG: This totally reminds me of how one of my ex-boyfriends would try to clap to, like, a band.

BARBER: Right.

CHANG: Like, he kind of gets it, but he's always a little bit off. All right.

BARBER: OK.

CHANG: All right, all right. Wait, wait, wait. Hold on, hold on. Let me try to recreate that (clapping). Want me to keep going?

BARBER: No. That's good.

CHANG: I could do this the whole rest of the episode.

BARBER: Well, like, I mean, I can hear your clapping. It seems pretty close, right? So, like, the researchers did this, like, over and over again with participants in this recent study, and they played subjects this, like, funky, irregular rhythm with beats spaced at sort of, like, random intervals. And then they would have the subjects respond, and usually, they would respond with this, like, more evenly spaced rhythm. And at the end, it sounded more like this.

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CHANG: (Clapping).

BARBER: Exactly. Right?

CHANG: Yeah, like sets (clapping) of triples. OK, so it's almost like our brain is trying to impose order on disorder - like, tidy things up.

OZA: Yeah. Exactly. And it's not just that we hear simple patterns. The scientists found that when we hear something kind of random, we instinctively impose a structure on it that sounds musical and a little rhythmic.

CHANG: That is so cool. And this varies across all cultures?

BARBER: So the researchers looked at people across 15 different countries - in Bolivia, Botswana, India, Mali, Indigenous populations in the Amazon and of course, college students in Boston, and they wrote about it in the journal Nature Human Behaviour. And across cultures, there was always this tendency to take these more random beat sequences and put them into a simpler, more ordered rhythm.

OZA: But those rhythms varied by culture. So, for example, dancers and musicians in Mali who performed this kind of music...

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OZA: ...When the researchers did the experiment with them, they instinctively came up with a rhythm that kind of sounded like the structure that they're already used to, and that held up for participants across the globe.

CHANG: That's so fascinating.

BARBER: But despite these cultural differences, there seemed to be this, like, universal bias towards a more simple, structured rhythm instead of the original random samples they heard.

CHANG: So our brains yearn for simplicity.

BARBER: Well, I. mean, researchers have a theory, which is that this could be a huge advantage for passing songs from one performer to the next. Because if the first performer makes a few rhythmic mistakes, the second performer will probably hear it the way it was intended to sound and play it without mistakes. So this phenomenon could have helped our ancestors pass on rhythms and songs and keep traditions going.

CHANG: That is so cool.

BARBER: Yeah. I think so.

CHANG: All right. I'm going to move on to our last topic - a satellite that tracks climate warming emissions. Tell me more.

BARBER: Yeah. So it's a story that's inspired a lot of, like, climate-related hope.

CHANG: Climate hope? Wow. OK. That's a rarity.

BARBER: Agreed. Agreed. OK. So on Monday, our NPR colleague Julia Simon was in Southern California watching this SpaceX Falcon 9 rocket launch.

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BARBER: And taking a ride on that rocket is a satellite called the MethaneSAT. It's a project led by the Environmental Defense Fund, and it's designed to detect methane, a gas that in the short term, can have climate effects even more harmful than carbon dioxide.

OZA: It's responsible for about one-third of human-caused global warming. And methane leaks into our atmosphere in a lot of ways, like when fossil fuels are produced. And what the oil industry calls natural gas is mostly methane. But it's been hard to pinpoint where exactly it's coming from.

CHANG: Wait, so how will this satellite help us identify these methane sources then?

BARBER: So it has these sensors specifically designed to detect the fingerprint of the methane molecule. For now, they'll focus on looking at emissions from the oil and gas industry. And the satellite can zero in on specific oil and gas producing regions like Texas or parts of Russia. And once it's fully operational in the coming months, it will send data back to Earth, and that data will be free to the public.

OZA: And we should add, there are other satellites that do this type of detection, but this new satellite should give a more precise and more public view of these polluters.

CHANG: But I have to say, like, other industries do produce methane, as well, like the agricultural industry. So why focus first on oil and gas?

BARBER: Yeah. The people behind the satellite say that it's strategic. Like, there are a relatively small number of companies in the oil and gas industry, and they have big budgets. And that will allow them to actually fix these leaks. So by making this data free to the public, the hope is that governments and other regulators can then hold oil and gas operators accountable.

OZA: Yeah. For example, the EPA made a rule last year that the oil and gas companies must monitor, detect and fix methane leaks when they happen.

CHANG: OK.

OZA: So the satellite could help with that.

BARBER: Ailsa, thank you so much for hanging out with us.

CHANG: Oh, totally. Anytime.

BARBER: You can also catch Ailsa on Consider This - NPR's afternoon news podcast. But before we head out, a quick shout-out to our SHORT WAVE Plus listeners. We appreciate you, and we thank you for being a subscriber. SHORT WAVE Plus helps support our show. And if you're a regular listener, we'd love for you to join so you can enjoy our show without sponsor interruptions. Find out more at plus.npr.org/shortwave. Shortwave.

OZA: This episode was produced by Michael Levitt and Rachel Carlson. It was edited by Viet Le and Christopher Intagliata.

BARBER: Brit Hanson checked the facts and the audio engineer was Josh Newell. I'm Regina Barber.

OZA: And I'm Anil Oza.

BARBER: Thank you for listening to SHORT WAVE from NPR.

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