NATURE PODCAST

Podcast: A mindset for success, and mercury in fish

Listen to the latest science news, with Noah Baker and Nick Howe.

This week, a mindset to improve school performance, and the complex story of how mercury accumulates in fish.

In this episode:

00:46 Growth Mindset

How a one hour course could improve academic achievement. Research article: Yeager et al.

11:47 Research Highlights

An extinct giant parrot, and hacking Manhattan’s traffic. Research Highlight: Polly wants many crackers: fossils reveal first known giant parrot; Research Article: Vivek et al.

13:42 Toxic Tuna

Methylmercury levels in fish may increase due to climate change and overfishing, despite declines in emissions. Research Article: Schartup et al.

19:15 News Chat

India’s proposed protections for fossils, and trust of scientists in the United States. News: India’s geologists champion law to protect fossil treasures; News: US trust in scientists is now on par with the military

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Transcript

This week, a mindset to improve school performance, and the complex story of how mercury accumulates in fish.

Host: Nick Howe

Welcome back to the Nature Podcast. This week, we’ll be hearing about how a psychological intervention could improve achievement…

Host: Noah Baker

And learning about the complexities of measuring mercury in fish. I’m Noah Baker.

Host: Nick Howe

And I’m Nick Howe.

[Jingle]

Interviewer: Noah Baker

I have a confession: I’m not particularly good at maths. I never have been. Now, that’s not to say that I’m really, really bad at it, like I know that three squared is eleven and that if you divide anything by zero you get forty-two, but it’s never been my subject, you know. But what if I thought differently at school? Instead of knowing that maths wasn’t my thing, what if I was encouraged to try again, to not accept that me and mathematics were just never going to tessellate? Could things have been different? Well, according to psychologist Carol Dweck from Stanford University, they might have been. She’s a proponent of a theory called growth mindset – a belief that attributes aren’t fixed. Instead of accepting that I’m just bad at maths, I could see my mathematical ability as something that could be trained and could grow, and that very process of changing my mindset could also change my performance.

Interviewee: Carol Dweck

And it doesn’t mean anyone can do or become anything, but it means everybody has the capability to develop their intellectual skills.

Interviewer: Noah Baker

That’s Carol. She’s published various studies over the years, exploring how growth mindsets could impact young people and this week in Nature, she and her co-authors are publishing their biggest and most rigorous study yet. Their experiment gathered data from a nationally representative sample – over 60 public secondary schools across the United States. Their goal was to deliver a growth mindset intervention which could be controlled and standardised. In their case, it was a self-administered online exercise. Here’s first author David Yeager from the University of Texas.

Interviewer: David Yeager

The students go to the school computer lab and then they read new content, they answer questions, they interact with an online activity. From the kid’s perspective, that’s the whole study, but then we researchers go back to the schools and obtain academic records at the end of their first year of secondary school, end of ninth grade.

Interviewer: Noah Baker

And they found that their growth mindset intervention did indeed had an effect.

Interviewer: David Yeager

A short, online growth mindset treatment improved core grades in the group of lower achieving students, which is students at or below the 50th percentile in their high school, by about 0.11 standard deviations.

Interviewer: Noah Baker

That equates to about 3% of students moving on to their next year of school, when previously they could have been asked to repeat the year. Carol and David also found that there was about a 3% increase in the number of students choosing to take advances classes in mathematics. Now, not everyone was affected by the growth mindset intervention. In fact, there were times when it had no effect at all and when it did, the effects weren’t huge. But Carol emphasised that in an educational context, all of this is relative.

Interviewee: Carol Dweck

We got about half the effect for the low achievers of the most successful past studies with no particular teacher training, with a self-administered program that took less than an hour and cost very little.

Interviewer: Noah Baker

Growth mindset theory is not without its opponents. Timothy Bates from the University of Edinburgh, for example, wasn’t completely sold on the study.

Interviewee: Timothy Bates

The thing that I’m most interested in is what did they actually do, and unlike most scientific papers, from this paper you couldn’t replicate this study because it doesn’t actually contain the materials, so I think a critical thing for researchers wanting to explore this in the next months will be to access those materials and dissect them to make a sort of parody case. One could give people the answers to the last three questions of an exam – that would be a very effective intervention. Children would then know three more answers but it wouldn’t generalise, it wouldn’t support any theory.

Interviewer: Noah Baker

The intervention used by Carol and David hasn’t been made public. They’re worried that people might try to commercialise it. However, they are making it accessible for free to educators who want to use it, and researchers like Timothy will be able to request access to the material so long as they sign a few disclosure agreements. This may go some way to tackling one of Timothy’s biggest reservations – studies like this are hard to reproduce.

Interviewee: Timothy Bates

It surprised us. We’ve had a PhD student working for the last for years on this, I’ve been doing work in the area for the last seven years, and the core papers in this field have been cited thousands of times – they’re among the very most cited papers in all of psychology –and yet when we started, there were no straight replications of those original studies in existence.

Interviewer: Noah Baker

David and Carol are both well aware of these criticisms, and in this study, they took a lot of steps to try to overcome them. In particular, they removed themselves as much as possible from the study. Here’s Carol to explain.

Interviewee: Carol Dweck

The researchers – us – were completely hands-off during the administration of the study, the collection of the data, the organisation of the data. Also, we had pre-registered hypotheses and analyses that were public and could not be changed. In addition, an independent set of statisticians analysed the data without knowing which group was the experimental group or the control group, the nature of the different variables, and they confirmed the results of our analyses.

Interviewer: Noah Baker

Here’s David.

Interviewer: David Yeager

The Nature paper should end questions about whether this effect is reproducible by third parties because of the lengths that we went to.

Interviewer: Noah Baker

But this wasn’t Timothy’s only concern. He also pointed out that, reproducible or not, the effect sizes in this study are very small.

Interviewee: Timothy Bates

Most people think that something that works, you could see it work in a child, and at least you should see the classroom, and this is an effect which is so small, you need thousands of people to see it.

Interviewer: Noah Baker

Unsurprisingly, Carol and David disagreed and highlighted that this isn’t the only approach. Here’s Carol.

Interviewee: Carol Dweck

We are not saying that a growth mindset intervention should replace other kinds of important school reform, but we see it as a coordinated effort.

Interviewer: David Yeager

An economist at Brown University, Matt Kraft, recently reviewed all available effect sizes from previous education RCTs at meta standard of rigour that would make them believable and laid out the distribution to say how much of an effect you expect at what kind of cost. The effects we show in targeted subgroups of students are among the largest from the entire population of effects that have been observed in previous RCTs. There may not be stronger even small-scale effects from studies that use rigorous randomised designs.

Interviewer: Noah Baker

That was David Yeager from the University of Texas at Austin. Before him, you heard Carol Dweck from Stanford University and Timothy Bates from the University of Edinburgh. You can find Carol and David’s paper over at nature.com. It’s been published open access so you don’t need a subscription. And if you’re an educator and what to try this yourself, you can find information about where to get hold of the intervention in that paper. While reporting this story, it became clear to me that it might be a little bit of time before the debate surrounding growth mindset is fully settled among academics, but is also became clear that ultimately, this is all about schools and how best to teach students, so I thought I’d also reach out to a teacher to get her take.

Interviewee: Theresa Ball

Yes, so my names Theresa Ball and I’m an Assistant Headeacher at Hammersmith Academy.

Interviewer: Noah Baker

Theresa’s school in West London has whole-heartedly embraced the growth mindset theory ever since the school’s foundation almost a decade ago. From her point of view, it carries a very compelling message.

Interviewee: Theresa Ball

I mean it’s the whole point of teaching. If people were just naturally good at things, there’s not really much point in trying to teach people and I think in schools now, there’s been a drive and a push towards teaching students how to learn rather than just the things that they need to learn. So, instead of just learning fact after fact, but learning skills that you can use in order to develop in subjects.

Interviewer: Noah Baker

Theresa was well aware that there had been some debate over growth mindset theory and was eagerly awaiting this latest study – she’d had a tip off it might be on the way. I asked her if she thought an online intervention like Carol and David’s could be a useful tool in her school.

Interviewee: Theresa Ball

I think that this would be a kind of nice thing to have and it would be an add on, but it would never replace all the other things that happen. I mean all these things have been dressed up with different phrases over the years but it still remains the same principle of trying to help students to be successful.

Interviewer: Noah Baker

Theresa did warn about the dangers of flashy scientific ideas leading teachers down the wrong path.

Interviewee: Theresa Ball

For a long time, schools have been very quick to jump on to ideas without researching them properly, but actually schools are tending to move away from that.

Interviewer: Noah Baker

Nowadays, she things that interventions like this would be popular, but subject to scrutiny by schools themselves before they were introduced as part of their policy.

Interviewee: Theresa Ball

I think schools would use it and try it out, maybe with a select group of students, and then see If it has an impact on that group of students compared to the rest of the cohort, but it certainly wouldn’t be the only thing that schools would do. It’s just not the nature of how schools operate.

Interviewer: Noah Baker

Ultimately, Theresa’s view was fundamentally a practical one.

Interviewee: Theresa Ball

We are trying to embrace kind of this research culture and so we are open about things and I think we’re open as well that growth mindset isn’t going to fix everything and for some students and some situations, it’s not going to be what we want it to be and then there’s something else that you might want to try. But I think as a principle, if the message that you’re sending out to people is if you try this and you stick with it and you don’t put a limit on what you can achieve and you don’t assume that people are naturally good at things, I don’t see why that’s ever going to be harmful to students in a learning environment where they have to do all these different subjects anyway.

Interviewer: Noah Baker

That was Theresa Ball from the Hammersmith Academy in London.

Host: Nick Howe

At the end of the show, we’ll be talking about how a new Indian law aims to protect fossils – that’s in the News Chat. Now, it’s time for the Research Highlights, read this week by Shamini Bundell.

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Shamini Bundell

Whether it’s the three-and-a-half-metre tall giant moa or the unfortunately meaty dodo, unusually large birds are often associated with islands. Now, scientists studying fossils from New Zealand have found an example of another extinct giant – a prodigious parrot that lived around 17 million years ago. The fossil parrot, that the scientists have inventively termed Heracles inexpectatus, stood at one metre tall and probably weighed around 7 kilograms. It’s the largest parrot ever found – more than twice as heavy as current title holder, the kakapo. Like the kakapo and the moa, both also from New Zealand, Heracles inexpectatus probably evolved its unusual size thanks to living in an isolated region with few natural predators. Big up that research over at Biology Letters.

[Jingle]

Shamini Bundell

If a hacker wanted to create a traffic jam, what would it involve? Well, researchers have calculated how many cars would need to be hacked in order to bring Manhattan to a standstill. The scientists simulated traffic conditions and road networks in Manhattan. They found that if around 30% of cars on the road during a typical midday in the borough were immobilised, it could cause gridlock. A cyberattack like this may sound far-fetched, but in 2015, two hackers showed they could take over a Jeep by tapping into its Wi-Fi. And while the authors admit jamming up Manhattan is a much taller order, they warn that just because something is difficult, doesn’t mean it can’t happen. Find that study over at Physical Review E.

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Interviewer: Nick Howe

Billions of people around the world rely on fish for nutrition and for good reason. They’re a great source of protein, vitamins and minerals. But fish are also the main route by which people are exposed to methylmercury, a toxin which is formed when mercury is released into the environment by various human processes. Ingestion of large amounts of methylmercury can cause heart problems and brain disorders. To prevent human exposure, an international treaty, the Minamata Convention, was introduced to prevent the release of mercury by humans into the environment. This effort has led to less methylmercury in the sea. You’d think then that there’d be less of it in fish too.

Interviewee: Amina Schartup

One thing we noticed was that depending on the fish species that people were talking about in their work, it was either the concentrations are going up or down or remaining flat, even though the atmospheric levels of mercury have been declining. So, the question was, why do we see all those different directions in terms of mercury levels in fish?

Interviewer: Nick Howe

This is Amina Schartup, a biochemist who looks at toxic chemicals in the environment. This week in Nature, she’s publishing a paper that’s trying to work out why people are seeing increases in methylmercury levels in some fish, even though the amount in the environment is declining, and how the concentrations in fish may change in the future. I gave her a call to find out more and started out by asking how she was answering these questions.

Interviewee: Amina Schartup

We wanted to construct a model that actually allows us to literally play around with different environmental parameters to see if seawater temperatures was part of activity levels in the ocean, how is that going to impact this particular fish mercury level versus another fish?

Interviewer: Nick Howe

So, what was this model based on?

Interviewee: Amina Schartup

The idea was just to build a fish from scratch, right. So, using mathematical equations, we will make a fish and have it grow in this mathematical universe we created for it and then it will eat other fish that are also robot math fish and then see how, depending on their diet and the conditions around that fish, how that is going to impact mercury levels.

Interviewer: Nick Howe

And so, what did you find by doing this?

Interviewee: Amina Schartup

As mercury levels in seawater have been declining and have recently plateaued due to regulatory efforts, we have noticed, at least in our model, that despite the decline in seawater concentration, we haven’t seen any mercury decline in tuna, in the bluefin tuna we’re working on. And actually, if we project the increases in temperature in the Gulf of Maine which is the region we’re working on, we see that the bluefin tuna mercury concentrations are going to increase despite a decline in mercury levels, which actually means that we also need to keep an eye on our carbon emissions and the implication of those emissions have on seawater temperature because even despite declining mercury levels, we may see an increase in mercury levels in the fish just driven by seawater temperature.

Interviewer: Nick Howe

And how exactly does an increase in temperature lead to an increase in mercury in the fish?

Interviewee: Amina Schartup

The reason we see an increase is when it’s warm, and these are for the most part cold-water animals, they are sensitive to temperature, so when the temperature of seawater increases a tiny bit, their activity also level increases, and so as their activity level increases, their consumption of food increases but they don’t grow fast enough to compensate for the fact that they’re consuming more.

Interviewer: Nick Howe

Right, okay, so when things get warmer, they eat more and they just end up accumulating more mercury in their system.

Interviewee: Amina Schartup

Right.

Interviewer: Nick Howe

Also in the paper, you talk a little bit about overfishing as well. What impact is that having?

Interviewee: Amina Schartup

Yes, so diet is quite important and depending on what a fish eats, it will have a different level of exposure to mercury. The issue with overfishing certain species is that if, for example, that particular species was low in mercury, like a herring for example, and you have another predatory fish that used to consume that herring but now you overfish the herring and so your other predatory fish decides it needs to eat something else. So, depending on what that predatory fish is going to switch to – is it going to be a higher mercury level fish or a lower mercury level fish – you will see either a decline or an increase in mercury levels in that predatory fish.

Interviewer: Nick Howe

So, in terms of thinking about sort of climate change action and things, is that what needs to be done then, in order to prevent such increases in the mercury concentrations in fish?

Interviewee: Amina Schartup

So, we often talk about climate change as this very abstract thing and it’s really hard to see what our daily implications can be for some people aside from extreme events. But this one was really trying to link the impact of climate change to all the other little things that we do in our daily lives, so it’s going to impact our plates and what we like to eat. It’s not just those physical things around us, it’s also in our food.

Interviewer: Nick Howe

That was Amina Schartup of the Harvard School of Engineering and Applied Sciences in the US. You can find her paper over at nature.com. Speaking of what’s over at nature.com, it’s also chockful of interesting new, which bring me, oh so smoothly, onto what’s coming next, which is of course the News Chat. This week, I’m joined by Heidi Ledford, one of Nature’s biomedical reporters. Hello, Heidi.

Interviewee: Heidi Ledford

Hi, Nick. Thank you for having me.

Interviewer: Nick Howe

Thanks for coming down to the studio. This week, we’ve got a story about a survey gauging people’s trust of scientists in the US. How are scientists faring, Heidi?

Interviewee: Heidi Ledford

Well, I have to admit, I was kind of surprised because it looks like scientists are faring pretty well. The percentage of Americans who say that have a great deal of confidence in science or in scientists, I guess I should say, has actually increased since 2016, so it’s up to 35%. It used to be just 21%.

Interviewer: Nick Howe

So, how are scientist doing compared to other public figures that may also be gauged on their trust?

Interviewee: Heidi Ledford

Yeah, they’re doing pretty well, actually. So, overall, the amount of confidence that the public has in scientists is comparable with public trust in the military which, in the survey at least, is one of the most trusted groups that they looked at.

Interviewer: Nick Howe

Okay, and was this true across the board or were there some people who trusted scientists more and some people who trusted them less?

Interviewee: Heidi Ledford

Yeah, I mean there were some differences there, particularly along party lines. So, in general, you could see a trend that Republicans tended to trust scientists less than Democrats. That may not be very surprising because you do often see, particularly when it comes to environmental issues and climate change, that the Democrats are more active on that front generally speaking than Republicans. There were also differences in how underrepresented minority groups felt about scientists, so black and Hispanic Americans, for example, tended to be a bit more sceptical, I’d say. I looked particularly at the medical researchers. The reason I focused on that is because there’s a fair amount of difficulty trying to recruit underrepresented minorities into clinical trials and one of the reasons that people give for that is that there is that scepticism, and you can see that there in the numbers that black and Hispanic respondents were more sceptical of medical researchers than, for example, white respondents were.

Interviewer: Nick Howe

And do we know if there was any difference between people who had a greater knowledge of science, like whether they trusted them less or more?

Interviewee: Heidi Ledford

Oh yes, so people with a greater knowledge of science overall tended to trust scientists more. I think you’d expect that.

Interviewer: Nick Howe

Not too surprising necessarily, but the overall picture is that trust in scientists is going up.

Interviewee: Heidi Ledford

It is. It appears to be. Truthfully, there aren’t statistical confidence intervals on these numbers but just if you look at the absolute percentages then yes, they have gone up.

Interviewer: Nick Howe

This seems like quite good news then for science in the United States.

Interviewee: Heidi Ledford

Well, it does, I guess, when you look at these numbers. It’s a little bit hard for me to match these numbers up with some of the public discourse about climate change or vaccines, things like that, but if it’s a sign of a trend of growing faith in scientists, maybe they will be listened to a bit more in some of these debates and maybe that could be a good thing. I guess one other point that could be drawn from this is that people do report a lot of scepticism of authority figures in general, and so one person that I talked to about these numbers said not only is confidence perhaps going up, but also you have to remember that not all of the scepticism is due to science. Some of it just due to general scepticism about authority figures and where information is coming from and potential biases and so forth. So, maybe there’s cause to be optimistic – maybe more optimistic than I happen to feel at the moment. Laughs.

Interviewer: Nick Howe

And we’re going to move on to what is hopefully another optimistic story, and there is a new law that is trying to be introduced in India to protect precious archaeological sites. Heidi, what’s the background to this? Why is such a law required?

Interviewee: Heidi Ledford

Yeah, India has a number of really interesting geological sites and fossil sites and so forth that currently aren’t being well protected by law. So, there’s a big push among Indian scientists at the moment to get lawmakers to institute something that will preserve these sites.

Interviewer: Nick Howe

I mean has there been any examples of where sites haven’t been protected and something’s gone wrong?

Interviewee: Heidi Ledford

Yes, there is. So, as one example, there’s this very cool, large dinosaur nest that had been discovered and they had even found the fossil of a snake that was coiled around one of the eggs, so it was this evidence that snakes were preying on dinosaur hatchlings perhaps long, long ago, but unfortunately, for a long time, there was nothing in place to protect those fossils and people raided the site and stole some of the eggs.

Interviewer: Nick Howe

So, people then are raiding these sites. Are there other reasons that these sites are in danger?

Interviewee: Heidi Ledford

Yeah, India is undergoing a period of really rapid development. I mean they’ve had some sites that are being threatened just by road expansion, for example. But there are building projects everywhere and some of those projects may compromise some of these sites.

Interviewer: Nick Howe

Is there just nothing in place to protect them at the moment?

Interviewee: Heidi Ledford

There’s sort of a patchwork of regulations in different states and so forth, but there’s not a coherent framework and certainly, there are many sites that are left without any real regulations. So, I think what some of these scientists are proposing would really bring a more uniform protection to these areas – I mean they’re talking about really hundreds of different sites – and they’re pushing to really institute some real consequences for damaging these sites, so imprisonment, for example, or large fines.

Interviewer: Nick Howe

So, the hope then that this law will make a difference, but I understand this isn’t actually the first time there’s been a push for this law. Why might this one in particular be different?

Interviewee: Heidi Ledford

Yes, they have tried this a couple of different times before and, to be honest, it didn’t go anywhere, but the hope this time is that they can establish a national authority that would help to establish geo parks that would promote tourism and that would provide some seed money to help get these regulations going.

Interviewer: Nick Howe

Well, we’ll have to see if this bill is more successful than the previous ones. Heidi, thank you for those updates. Listeners, if you want to find out more about those stories and others, head over to nature.com/news.

Host: Noah Baker

And that’s all for this week. But if you’re ears aren’t quite tired of science just yet, then don’t forget to check out our sister podcast, Science Talk from Scientific American. You can find that in all the usual podcast places. I’m Noah Baker.

Interviewer: Nick Howe

And I’m Nick Howe. See you next time.