SACHA PFEIFFER, HOST:
Time now for our science news round up from Short Wave, NPR's science podcast. With me are Rachel Carlson and Emily Kwong. Hi to both of you.
RACHEL CARLSON, BYLINE: Hi.
EMILY KWONG, BYLINE: Hi, Sacha.
PFEIFFER: So you've brought us three science stories that caught your attention this week. What are they?
CARLSON: How electricity could help you measure and make a better cup of coffee.
KWONG: Then how to analyze your dreams like a scientist.
CARLSON: And a surprising secret behind scorpions' weapons.
PFEIFFER: Ah, coffee, dreams and scorpions. I like this.
KWONG: Yes.
CARLSON: Natural combo.
KWONG: (Laughter).
PFEIFFER: So I am one of the rare people who don't start my day with coffee, but since so many people do, start us off with your coffee science story.
CARLSON: OK. First, I'm impressed with you, honestly.
PFEIFFER: (Laughter).
CARLSON: But here's the thing about coffee. It's extremely variable. Visit the barista at your local fancy cafe, and they'll tell you the flavor of your cup is affected by so many different things, like the coffee beans, the way those beans were fermented and roasted, the temperature it's brewed at, the chemicals in the water that you use to brew it.
KWONG: Now you're making me want coffee. And even though there's a technique the industry uses to measure the concentration of coffee, that misses those other aspects of flavor, like acidity or brightness or fruity or sweety or nutty notes that coffee drinkers care about, which causes all kinds of problems.
PFEIFFER: All right, when we say problems, what kind of problems related to coffee?
KWONG: Yeah. With, say, the degree of bean roasting. You know, coffee consumers may be familiar with roast type - a light medium or dark roast. But a light roast from a national coffee chain may be considered a dark roast by your local gourmet coffee house.
CARLSON: So scientists at the University of Oregon wanted to see if they could change that. They used a tool that's usually used to measure the charge in batteries to assess the flavor of coffee.
KWONG: Sacha, they basically ran voltage through a cup of coffee.
PFEIFFER: (Laughter).
KWONG: And based on the electrochemical response, the scientists found they could get a quantitative sense of the acid levels and the intensity of a cup of joe. Basically, they could tell how strong the coffee was and how dark the roast was.
CHRISTOPHER HENDON: You're just basically sticking two pieces of conductive metal into coffee, and then the coffee acts as a resistor. And at different voltages, you have different molecules reacting with that applied voltage.
CARLSON: This is Christopher Hendon, a chemistry professor and a coffee expert, and he's the lead researcher on a study about this in the journal Nature Communications.
PFEIFFER: You know, because you said they use a tool that's usually used to measure the charge in batteries, I feel like there's definitely a coffee battery acid joke here.
CARLSON: Totally. Totally.
PFEIFFER: But tell us how voltage measures what, and is it actually a useful measurement to coffee makers?
CARLSON: It is, yeah. Based on the tests they ran, this method was at least as good as human experts at telling when a roast is bad. And Christopher is an expert. He used to coach in the competitive coffee circuit.
PFEIFFER: (Laughter).
CARLSON: But, Sacha, just to be clear, this doesn't mean that coffee tasting is going to be outsourced to lab devices. But Christopher is hoping it could help the industry develop a more numbers-based way to describe those tastes, sort of like the International Bitterness Units in beer.
HENDON: In the beer industry, they have IBU, which is somehow inferring how hoppy a beer is going to be, and they put a number on it. And so there's nothing that prevents us from implementing something very similar based on this measurement on coffee bags.
KWONG: I didn't know IBU existed, by the way.
CARLSON: I didn't either. I had no idea.
KWONG: I'm going to use it 'cause I don't love hops, you know?
PFEIFFER: And I didn't know there was a competitive coffee circuit. So all of us have some Googling to do later. All right, so we started with coffee, which is how many people start their days. Now let's go with how many people end their days - dreams.
KWONG: Yes.
PFEIFFER: Tell us about the dream research you're looking into.
KWONG: Yes. So a recent study in the journal Communications Psychology has some new insights for all of us dreamers on how personality and behavior traits may predict the types of dreams we have, because some people's dreams are more vivid and others' are more fragmented.
PFEIFFER: Yeah, and I definitely fall in the category of people who can wake up and having had - just had a very intense dream, but then you forget it so quickly. So given that dreams fade quickly, how do scientists study them?
KWONG: Yeah. So for two weeks, over 200 participants recorded voice memos of everything that was going through their mind just before they woke up. They also recorded their thoughts during the day and they filled out questionnaires to assess different aspects of their personality. They also wore devices to track their sleep and waking patterns in bed.
CARLSON: Researchers at the IMT School for Advanced Studies Lucca in Italy then analyzed all of this data to see if any patterns emerged between who people were and the contents of their dreams.
PFEIFFER: Yeah. And tell us, what patterns? How does personality affect dreaming?
KWONG: Yeah. There were some stable patterns. So participants more prone to mind wandering tended to report more bizarre dreams, particularly dreams that rapidly change scenarios, so like you're in a hospital. You're on a desert. You're on a beach. What's happening? Whereas people who assign more value and meaning to their dreams tended to have richer ones, more vivid and perceptual dreams.
CARLSON: Lead author Valentina Elce also found people who self-reported having better sleep quality also had more immersive dreams. And this aligns with an idea in psychology that dreams are guardians of good sleep.
VALENTINA ELCE: Maybe the fact that we experience this very vivid dream is a way of the brain to protect our sleep, to let us into immersive worlds where we can be less affected by the external environment.
KWONG: Valentina also is the first to acknowledge that because the study depends on the reports of the participants, it has its limitations. They're not studying dreams, right? They're studying reports about dreams.
PFEIFFER: Yeah. Did she have any advice, beyond just write it down quickly, how you can remember your dreams better?
CARLSON: She did. Record your thoughts, she says, the moment you wake up in the morning. I actually do this almost every morning when I remember.
PFEIFFER: Oh, really?
CARLSON: And Valentina said a voice recording could actually be better than writing it down to get all those juicy details in before the dream floats away.
PFEIFFER: Good advice. All right, for our third item, something all of us hope will never be in our dreams, and this is scorpions...
KWONG: (Laughter).
CARLSON: Yes.
PFEIFFER: ...And their anatomical weaponry. Tell us about this.
CARLSON: So scorpions have two weapons of choice - their stingers to inject their prey with venom or death by claw. And it turns out these weapons are fortified with metal, like zinc, manganese and iron.
PFEIFFER: Oh, that is so interesting. Metal that, I guess, gives them strength. Is that the idea?
CARLSON: Yeah, that's part of the idea. It's a very heavy-metal trait, you could say.
PFEIFFER: (Laughter).
CARLSON: And researchers wanted to find out why these metals might be in scorpion weapons and whether a scorpion's hunting style could have anything to do with it.
KWONG: Yeah, because some scorpions mostly hunt with their stingers, whereas others rely more on their claws. For example, the Trinidad thick-tailed scorpion tends to favor its stinger.
PFEIFFER: So is the idea that scientists are trying to figure out if whatever weaponry the scorpion uses, there's more metal in that part of their body?
KWONG: Exactly, yes. That was the question. So scientists used microscopy and micro-X-ray imaging to look at 18 species across the scorpion tree of life.
CARLSON: They found that iron, for example, was only found in scorpion claws and manganese was only found in scorpion stingers. The researchers think that's because manganese could help hardened stingers while maybe iron protects their claws from wear over time.
KWONG: And all of that could support the idea that different metals may be related to different hunting methods.
PFEIFFER: That is so fascinating, but I am going to ask you the applied science question. So where do researchers want to go with this, and how do they think that could inform human understanding of the world?
CARLSON: Right. Well, it turns out there are thousands of scorpion species. So future research could and probably should look at even more scorpions to see how these patterns play out. And the researchers said that one day, it could be applied to things like materials science, like trying to mimic scorpion stingers or find ways to build their hard shells.
PFEIFFER: So interesting.
CARLSON: Yeah.
PFEIFFER: That is Rachel Carlson and Emily Kwong from NPR's science podcast Short Wave. Subscribe now for new discoveries, everyday mysteries and the science behind the headlines. Thanks to both of you.
CARLSON: Thanks, Sacha.
KWONG: Thank you so much.
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