Nature Podcast

This is a transcript of the 20th September 2012 edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (, which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to

Geoff Brumfiel: This week, can we all just get along? Actually, yes we can.

David Rand: People seem to be predisposed towards cooperation, so, it's like people's first instinct is to cooperate where rational thought makes you selfish.

Kerri Smith: And does the brain ever rest?

Chris Miall: Not unless you're either dead or probably very deeply anesthetized. At all other stages, including when you're asleep, there does seem to be quite a lot of brain activity.

Geoff Brumfiel: Plus clever parrots and memory boosts in the highlights. This is the Nature Podcast. I'm Geoff Brumfiel.

Kerri Smith: And I'm Kerri Smith.


Kerri Smith: From the work place to the global environment, from politics to charities, human society is to a large extent based on people working together for a common good. But cooperating like this is costly for individuals. So, why are we usually willing to cooperate and how do we decide to help others rather than act selfishly. These are questions that puzzled David Rand at Harvard University. He has been cooperating with some other Harvard folks to explore the cognitive basis of cooperative decision making and he spoke to Charlotte Stoddart. Nature 489, 427–430 (20 September 2012); Nature 489, 374–375 (20 September 2012)

David Rand: For a long time when biologists and social scientists studied cooperation it was mostly from a behaviour perspective, it was saying what can you do to make people cooperate, you know, how can you set systems up so that evolution would favour cooperation but there wasn't that much looking at what's actually going on inside the heads of people when they're cooperating. So, in this study, we tried to really sort of start delving into the actual sort of, cognitive psychology of what's going on inside people's heads when they are faced with social dilemmas.

Charlotte Stoddart: So, if I was taking part in your study what would I have to do?

David Rand: So, we use a very simple experimental game, it's called the public goods game. If you were participating what you'd do is you would be put in a group with three other people and you each get some money and you choose how much to keep for yourself and then how much you want to contribute to the group where all of the contributions would be doubled and then split equally among everyone. The key idea is there is this tension between what's good for you and what's good for the group.

Charlotte Stoddart: Okay, so how did you use the game then to look into cooperation and workout how people were deciding whether or not to cooperate?

David Rand: So, what we did is we basically looked at people that were making the decisions using a more intuitive mindset versus a more sort of a more rational mindset and compared their behaviour. So, one way of doing it is we just let people make whatever decision they wanted and we compared the people that responded quickly to the people that took a long time and we found that the fast responders were significantly more generous than the slow responders. And then we did other things like we forced people to go fast and saw that increased in their contribution have forced them to go slow and it decreased it.

Charlotte Stoddart: Right and you're assuming here that if people respond quickly or if they're forced to make a decision quickly, then they're acting on their intuition and if they take longer or they're given more time then they're more reflective.

David Rand: Right, that's a pretty common methodology in social and cognitive psychology but to really make formal that link that what is going on is the intuition versus reflexion, we have the last experiment where rather than using decision time what we do is we really primed them specifically about intuition or about reflexion and showed that it had the same effect.

Charlotte Stoddart: So, what are we learning about cooperation from that?

David Rand: What we're learning from that is that people seem to be predisposed towards cooperation. So, it's like people's first instinct is to cooperate where rational thoughts make you selfish.

Charlotte Stoddart: If you're right and we are intuitively cooperative, does this mean that cooperation is innate, that it's somehow hardwired into our genes?

David Rand: Our study doesn't really directly speak to that but I think that we provide evidence that that's not the case. In daily life where you've repeated interactions and there is reputation and there is the threat of sanctions, all these kinds of things make it advantageous for you to be cooperative. So, you just kind of get used to cooperating because it's a good strategy. And so with that in mind, we did a sort of experiments where we showed that people that sort of experience the world around them as a cooperative place, show the cooperative intuition that we talk about, whereas people that come from places where they don't experience the world as cooperative, they actually don't have cooperative intuitions.

Charlotte Stoddart: If we take this to the real world now, we're often encouraged to reflect before we make decisions, and if we think in particular about the United Nation's process where they're trying to get international collaboration, that's negotiation, lots of time for reflection, and so your research sounds like really bad news for those kinds of processes.

David Rand: Yeah, it is a little bit unsettling, I mean, particularly as academics, you know, we're all about rational thought and reflection and things like that, but one thing that it certainly seems to suggest is that if you're trying to make appeals to people to get them to be more cooperative, it may not be a good idea to use sort of rational arguments with lots of facts and statistics and things like that because that may shift them into a more analytical mindset, which then can lead to them being more selfish.

Kerri Smith: David Rand there. Find his results at Coming up shortly, what the brain is doing when it's at rest.

Geoff Brumfiel: But first, that story of making the most of excess heat. Thermoelectrics do exactly what their name says. They take heat, thermo and turn it into electricity. The potential applications are enormous. Waste heat from industry, car exhaust, just about anything you can think of could be recycled to make power. But current thermoelectrics aren't efficient enough to be practical. All that may be about to change because, Mercouri Kanatzidis has just developed a new very efficient thermoelectric. I called him at Northwestern University in Illinois to learn what makes this new material special.

Mercouri G. Kanatzidis: So, what has happened in the past 8 to 10 years, there has been a paradigm shift in how people think about these materials. Before that, everybody was thinking that these materials have to be single phase pure compounds. However, with the previous paper in 2004, we saw that when you put nanoscale crystals inside the thermoelectric matrix, if they are properly chosen and well oriented, the inter spaces between the nanocrystals that are embedded in the matrix, in the matrix can scatter phonons strongly; phonons scare the heat and reduce the thermoconductivity while at the same time, the electrons are not affected very much and they go sort of and this is the key to get a thermoelectric to work, we have to have electrons going through in a very facile manner, whereas phonons are impeded.

Geoff Brumfiel: So, the general idea here is that phonons, you've mentioned here, these are just vibrations in the material or heat I suppose in the materials, another way to think of it, are being bounced around and if you have these crystals in there then you actually you're capturing, you're harvesting more of that heat and allowing it to be converted to electrons, is that basically, sort of, the idea?

Mercouri G. Kanatzidis: So, you want heat to push electrons from the hot end to the cold end. You don't want heat to go independently via another path, and make its way to the other side. So, you want to block the heat that independently by itself is trying to reach the other side and get it to push electrons instead. So, these crystals are delaying the heat from travelling through. Instead, the heat stays at the hot end and does the pushing.

Geoff Brumfiel: So it's an electrical conductor and a thermal insulator.

Mercouri G. Kanatzidis: Insulator yes exactly.

Geoff Brumfiel: So, I wonder if you could just give us sort of a sense of how efficient this material is, like let's say you coated your car's exhaust system with it, I mean, how much power could you get out, have you done any sort of calculation like that?

Mercouri G. Kanatzidis: Yeah, we have. Nanostructuring takes you to the range of between say 13 to 15%, it's a huge boost when it comes to energy. We're using what we call hierarchical architecture, where we are impeding heat flow on three different scales; the atomic scale where we introduce disorder in the crystal structure, the nanoscale where we use nanostructuring to impede another part of the phonons that actually make it through. Then we introduce the mesoscale, where we make the grains small enough to have the same dimensions almost, the wavelengths of those, long wavelength phonons that actually do make it through even despite the nanostructuring, and we essentially block a very large fraction of the phonons back through.

Geoff Brumfiel: Just to say it again, the phonon spectrum is essentially sort of the spectrum of different heat energies travelling through the material. So when do you think I mean, thermoelectrics might start getting used generally?

Mercouri G. Kanatzidis: I think the materials that we have today are good enough for applications. What we report is the highest performance ever for the thermoelectric material in something that is scalable and relatively low cost. My belief is in about 2 to 3 years, we will have something.

Geoff Brumfiel: Mercouri Kanatzidis whose material could also be used to harness the heat from the sun, he says. Time for the research highlights now, so here's Charlotte Stoddart with the best of science outside Nature this week.


Charlotte Stoddart: Not content with mimicking what we say, parrots have mastered the art of reasoning too. They can figure out the presence or the absence of hidden objects using indirect evidence, a skill previously only seen in great apes. A team at the University of Vienna got six African grey parrots to guess which of two containers contained an object after they rattled one of them. Even when they shook the empty container and there was no sound, the parrots picked the right one. Relying on sounds to infer things may be more important to parrots than to other animals that have failed the same test - like dogs and monkeys. The paper is published in the journal, Proceedings of the Royal Society B. Nature 489, 338 (20 September 2012)Prompting rats to remember an experience during sleep can boost their memory of it. A pair of scientists at MIT trained rats to run either left or right when they heard one of two sounds. They monitored the response of neurons in the rat's hippocampus, the part of the brain that forms and stores memories. As the rats slept, the researchers played the sounds again. The noise triggered the rats to recall the task during their naps. The findings echoed recent experiments in humans showing that playing in cues during sleep can strengthen memories. Find that paper in the Journal Nature Neuroscience. Nature 489, 338–339 (20 September 2012)

Kerri Smith: Now Geoff, you can help me with this next topic. I want you to keep your eyes open, relax and try not to think of anything. Nature 489, 356–358 (20 September 2012)

Geoff Brumfiel: Okay here it goes. (Man, the podcast studio wall looks nasty, I think there's mould growing on it, I don't know where that came from. Mould is so weird it doesn't even need sunlight, isn't it a plant, no wait that can't be, bread might be mouldy, I need milk, I have to pick up more bread) (overlapping words)

Kerri Smith: Exactly, difficult isn't it, well neuroscientists haven't generally been interested in what your brain is doing in these idle moments. Usually they like to give their study volunteers a mental workout. While they scan your brain, they give you a job to do, a scene to search for faces or some numbers to add up. The assumption is that in the time between these tasks not much of anything is happening. But what neuroscientists are now finding is there's always something going on your brain.

Geoff Brumfiel: Even mine?

Kerri Smith: Even yours Geoff and even when you're asleep or otherwise idling or thinking about mould. In fact, the brain never rests.

Chris Miall: Not unless you're either sort of dead or probably very deeply anesthetized.

Kerri Smith: That's Chris Miall, who studies resting brain activity at the University of Birmingham in the UK.

Chris Miall: At all other stages including when you're asleep and including under light anaesthetic, there does seem to be quite a lot of brain activity.

Kerri Smith: About a decade ago, some neuroscientists using brain imaging began to look at the activity they were recording between the tasks they gave people. They would usually discount this stuff in their analyses assuming that all was quiet, but they found these very slow oscillations in their data that looked meaningful. When they looked more closely, they could see networks of brain areas connected by this activity, dubbed resting-state networks. Now scientists are interested in what this activity is for.

Chris Miall: Well, I think that's a million dollar question really, we don't really know and there's lots of different alternative ideas.

Kerri Smith: When people first started studying resting-state networks, it seemed like something mysterious and profound. Here's Michael Greicius from Stanford University, who's been studying resting brains for a decade.

Michael Greicius: When I saw these cortical networks, I started getting excited, as though we'd sort of landed on, you know, the stream of consciousness or something, this is ongoing conscious activity. After a couple of years, I was sort of disabused of that notion for few reasons. One is that basically all of these networks, 15 or 20 or more depending on how thinly you slice your data are, sort of, up and running at the same time. So it seems a little unlikely that you could be, you know deep in your memory network, while also in your language network and in your working memory network all at the same time. But I think, I need a bigger sort of argument against the hope that I had initially was that really most or all of these networks are present and pretty readily detectable in late stages of sedation and also at the late stages of sleep. And I just intuitively didn't seem like a good fit for ongoing conscious processing.

Kerri Smith: And when scientists looked in the brains of monkeys and rats, they found the same thing. Lots of slow activity in various brain networks that they were used to seeing activated during tasks. Over the past few years, scientists have come up with some ideas about what this resting activity might be doing for the brain.

Chris Miall: One of the main theories is that because you're not doing anything else, you're just in a sort of moment of introspection, so you might just be thinking about what you're doing while these scientists are recording your brain activity or you might be remembering, you know, what you had been doing earlier in that day. An alternative theory is that you actually sort of, the brain is in a state preparedness for what might come along in the future. So you might have this ongoing activity so that you can respond to any new challenge or any new task or any new stimulus that comes in. And then there are other theories including one that we propose that some part of that resting activity is concerned with the sort of background manipulation of prior information. We know that if you learn something, the brain processes that information for a few hours or a day afterwards and sort of turns this from short term memory essentially into a long term memory. And that may also contribute to what we measure when we measure resting-state.

Kerri Smith: So a little housekeeping, a little learning which breaks the question, could we boost this activity and make the brain better at those things?

Chris Miall: Well, it's entirely possible and in fact there is some evidence that you can boost that memory consolidation process by brain stimulation. I don't think anybody has yet looked to see whether or not it's a sort of a necessary causal effect that the stimulation changes the resting-state, that changes the memories, but that would be the implication.

Kerri Smith: One nearer term goal might be in the clinic. Resting-state scans are easy to sit through and they could provide useful information for clinicians diagnosing disease.

Michael Greicius: One nice thing about resting-state fMRI is that a patient say with mild Alzheimer disease who had a lot of trouble performing a memory task or a language task in a scanner is for the most part able to sit, you know, through the eight minutes of a resting-state scan allowing us to get a nice look at the networks in the brain and so the hope is that we can take a single subject, identify at a time the network that we're interested in, so for example, an Alzheimer disease, this fault mode network, which has been linked to memory and then quantify if the connectivity between two key nodes in the network, where the overall connectivity between all the nodes in a network and compare that to some for example, you know standard library of healthy control subjects. So that we'd have a number of connectivity within this memory network, you know and below a certain level, we'd say this person is likely to have Alzheimer's disease or likely to progress to Alzheimer's disease.

Kerri Smith: That was Michael Greicius of Stanford and before him Chris Miall at Birmingham University in the UK. And there's more to learn about resting brains in a feature in Nature this week.


Kerri Smith: The news chat this week comes from Washington, D.C. where Ivan Semeniuk is waiting for us, Hi, Ivan.

Ivan Semeniuk: Hello there.

Kerri Smith: Now when it comes to human evolution, geneticists and archaeologists haven't always agreed, have they and this is the subject of the first story in the news section this week.

Ivan Semeniuk: Absolutely. I mean, there's no doubt that genetics has in a sense revolutionized our understanding of human evolution prior to, you know, the advent of genome sequencing, we really were relying just on the fossil record, on the bones that anthropologists could dig out of the ground. Those bones have been, you know, obviously important in pointing the turning points to human evolution and to human ancestors, but now we have this independent means of looking at, you know, when the various splits occurred and when branches of the human family tree moved out of Africa for example. But there's a problem and the problem is that, you know, these two independent lines of evidence don't always agree and it's been a bit frustrating that there have been times where it seems as though, events like for example the separation of the Neanderthal line from the human line, the gene seems to suggest it's a more recent occurrence and the fossil record shows something that happened much much earlier. So now there's a new approach to this that has helped these two independent clocks or these two independent lines of evidence come into some agreement, so it's a big step forward.

Kerri Smith: And this step has to do with re-estimating the mutation rate, the amount of changes in the DNA of the human genome over time.

Ivan Semeniuk: That's right. That's the key to the DNA clock. It's just understanding how rapidly DNA mutates. And in the past that's been done by comparing human DNA with other contemporary primates and trying to estimate, you know, how many changes would have had to have occurred since we branched off from those other primates and that gives an estimate of the rate of mutation, you know, per letter in the genome sequence, something like once every billion years per any individual letter. But it turns out that that number has been refined quite a bit and it served to slow down the DNA clock. The new evidence comes from the fact that now dozens and dozens of humans have been sequenced, not just individuals but families and actually what researchers have found is that the mutation rate is about half as fast as they were originally estimating which means that in a sense it brings the DNA clock back into line with some of these fossil finds.

Kerri Smith: So it's clearing up then, some controversies where these dates hadn't matched in the past?.

Ivan Semeniuk: I think so and I think that's a big relief and also, you know, by removing some of these paradoxes and contradictions I think we're starting to see the human story come into focus.

Kerri Smith: So harmonious agreement then, from geneticists and archaeologists there. Now some less happy news, less harmonious news from the US, where it's been one of the worst years yet for West Nile virus.

Ivan Semeniuk: That's right. So, this virus first appeared in the US, in North America, I think in 1999. It was a great concern in the early 2000s, subsided a bit, and I think it's really caught most people by surprise. There was some warning of it earlier this year, but there's no doubt, that this has been the worst year so far for West Nile over 2600 cases so far, and over a hundred deaths, so, you know, obviously that's a concern for public health officials. We've been reporting this along the line, but we have a story this week that looks at a different angle, which is, you know, most public health, you know, methods or responses focus on the immediate threat, you know, West Nile is basically a mosquito-borne virus, the reservoir is in birds that migrate up and down North America. You know for most people, it's an illness that they survive and then move on with their lives. For a few it becomes acute and sometimes deadly. But increasingly researchers are beginning to look at longer term effects, perhaps some of the many thousands of people who have suffered mild cases of West Nile virus may unfortunately have consequences for their health down the road and one area in particular that one researcher is looking at, one that we focused on is the possibility that kidney problems may follow years after a West Nile infection.

Kerri Smith: And I suppose it's the case with some viruses that they do have these long term effects, but that wasn't known for West Nile virus previously.

Ivan Semeniuk: No, I mean, there are hints, for example, there are traces of the virus in the urine of lab animals, long after they've been exposed, but the question there has always been, you know, does that mean the virus is taking refuge in the kidneys and active there or is it simply that it's being filtered out by the kidneys. So there's this back and forth about whether this is really something that's going on or not.

Kerri Smith: Now moving on from the transmission and the kind of moving around of the West Nile virus to moving around lab animals, this is something we've covered before, but it's getting steadily harder for lab animals to build up their air miles, isn't it?

Ivan Semeniuk: That's right. So this is partly being driven by one advocacy group in particular, The People for the Ethical Treatment of Animals. So, they have an announcement this week, the two largest cargo carriers, FedEx and UPS have both now committed to no longer transport research mammals and in the case of UPS, they're also actually also considering a further step which is to restrict all animal transportation altogether, that would include even insects and amphibians. So, there are some real impacts here but there's also a larger issue. It definitely means that you know research advocates who are trying to make the case that some animals are required for science are I think failing to make the case.

Kerri Smith: Just for now, what is the scale of the problem, I mean, how many researchers or how many labs do rely on air freight for animals?

Ivan Semeniuk: Well, it's actually very difficult to tell because not surprisingly, you know researchers and companies who provide research animals are not particularly forthcoming about their practices. Now in larger countries, it may not be such an issue. In the United States for example, most research animals are actually transported by ground, but even so, some of the lab mice, kind of very specialty model animals, are transported by air and so this kind of action, there is a real effect for some people and potentially larger effect if fewer and fewer avenues are available for lab animal transport.

Kerri Smith: All right, so that's the story that we've followed in the past, and will continue to follow as it develops. Ivan Semeniuk thank you very much.

Ivan Semeniuk: Thank you Kerri.

Geoff Brumfiel: Next week, we've got regenerative mice and then the run-up to the US election in November, a plea for a more science friendly congress. I'm Geoff Brumfiel.

Kerri Smith: And I'm Kerri Smith, science's best friend.