NATURE PODCAST
31 October 2018

Podcast: Mood forecasting technology, and where are the WIMPs?

Listen to the latest science news, brought to you by Benjamin Thompson and Charlotte Stoddart.

This week, the role that mood forecasting technology may play in suicide prevention, and a 'crisis' in dark matter research.

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In this episode:

01:01 Where are the WIMPs?

A dark matter particle is proving illusive, what does this mean for physics? Review: Bertone & Tait

07:04 Research Highlights

What decades of dead salmon do to trees, and space travel’s effect on the brain. Research Highlight: Salmon-hurling scientists enrich an ecosystem; Research Highlight: Space crews’ grey matter shrivels during long stays in orbit

09:13 Mood forecasting technology

Could technology help predict when people will experience suicidal thoughts? Feature: Happy with a 20% chance of sadness

15:20 News Chat

Electrical stimulation helps people with spinal-cord injuries to walk, and a new use for an established chemistry technique. News: Three people with spinal-cord injuries regain control of their leg muscles; News: ‘Why didn’t we think to do this earlier?’ Chemists thrilled by speedy atomic structures

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doi: https://doi.org/10.1038/d41586-018-07258-4

Transcript

This week, the role that mood forecasting technology may play in suicide prevention, and a 'crisis' in dark matter research.

Host: Benjamin Thompson

Welcome back to the Nature Podcast. This week, we’re wondering where are the WIMPs?

Host: Charlotte Stoddart

And can technology be used to predict moods and save lives? I’m Charlotte Stoddart.

Host: Benjamin Thompson

And I’m Benjamin Thompson.

[Jingle]

Host: Benjamin Thompson

Well, listeners as I’m sure you heard from that intro, this week I am delighted to announce the return of the longest serving member of the podcast team. Welcome back, Charlotte.

Host: Charlotte Stoddart

Thanks, Ben, for making me feel so old! No, seriously it’s great to be back.

Host: Benjamin Thompson

Well, it’s great to have you back, and for our first story this week we’re going to have a short history lesson. Now, not so long ago – in the 1980s in fact – it seemed like the big questions in physics would soon be tied up into a neat little bow. Astronomers had realised that the Universe must have a whole load of mysterious matter in it that we can’t see, which is called dark matter. At the same time, particle physicists were puzzling over why fundamental forces had such different strengths, and in particular why gravity was so weak. Handily, there seemed to be a solution to both problems in the form of hypothetical particles known as weakly interacting massive particles or WIMPs. So, researchers around the world set out in search of these WIMPs but more than 30 years later, every hunt for the wonder particles has returned empty-handed. Reporter Lizzie Gibney spoke to Gianfranco Bertone about the crisis that’s now unfolding in the field. She started by asking him what we’ve learnt so far about the elusive WIMPs.

Interviewee: Gianfranco Bertone

Well, we actually made an enormous progress in the sense that we’ve ruled out many, many possible models, and in particular there is a strong tension on the fundamental idea at the origin of the whole WIMP candidates, which was that these particles could explain at the same time the dark matter on very large scales in the Universe, but it could also address some of the most fundamental problems in particle physics. Now that we know that that connection is not that strong as we thought, we can generalise our searches, you know, search for particles which are much larger or much more massive than the particles we’ve searched for so far.

Interviewer: Lizzie Gibney

And so, the searches themselves have in a way been successful. They did what they were supposed to do, it’s just that what we were looking for isn’t there.

Interviewee: Gianfranco Bertone

Exactly, it was a very interesting hypothesis and we are testing that hypothesis. The fact that we’re not confirming the existence of these particles is not a failure of science, but it’s actually a triumph of the scientific method. We know that these particles do not exist in that particular form, and we know how to extend our searches in order to test the different hypotheses about the nature of dark matter.

Interviewer: Lizzie Gibney

Okay, so weakly interacting massive particles seemed like, theoretically at least, a wonderful idea. All the results have come out negative. Where do we go from here?

Interviewee: Gianfranco Bertone

Well, there’s a plethora of other possible explanations for the nature of dark matter. Very popular alternatives are so-called axions – particles that rise in the context of the physics of quantum chromodynamics. Then there are other particles called sterile neutrinos. So, these are again similar to neutrinos but have different types of interactions and they don’t interact almost at all with standard model particles. So again, these would be a perfect dark matter candidates.

Interviewer: Lizzie Gibney

What are some of the experiments that we should be doing to look for some of these new kinds of candidates? How will the hunt change as a result of that?

Interviewee: Gianfranco Bertone

I think we’re going to learn a lot in the next decade by exploring astronomical and cosmological surveys so just by looking at how matter behaves on very large scales. Does it interact with itself? Does it interact with other particles in the Universe? The other field of research that we can exploit is that of gravitational waves, and we can actually test really some fundamental ideas, for instance, is it possible that dark matter is made of black holes?

Interviewer: Lizzie Gibney

And there’s another slightly more radical explanation for dark matter that, certainly from a journalist perspective, seems like it’s been growing in prominence, which is that maybe dark matter doesn’t exist at all and we’ve just misunderstood how gravity works somehow. Is that an idea – I think they call it modified gravity – is that something that you’ve seen grow in prominence in the scientific world as well?

Interviewee: Gianfranco Bertone

Modified gravity is an excellent idea, as a matter of fact, in principle. Modified gravity was invoked as an explanation for the dark matter problem in the early 80s, at the same time when weakly interacting massive particles were proposed as an explanation for the very same type of phenomenology. The problem is though, a lot of additional evidence has accumulated and in particular we use the cosmic microwave background, this kind of relic radiation that is produced in the early Universe, and unfortunately modified gravity theories have very little to say about it.

Interviewer: Lizzie Gibney

So it does seem like dark matter is still likely to be out there somewhere, but we’ve been looking for it for 30 years now. What’s the mood like among physicists when negative results just keep coming up? How do people feel at the moment?

Interviewee: Gianfranco Bertone

I would say that there’s a growing sense of crisis in the field of dark matter studies, especially because we haven’t found the most popular candidates that we have searched for, for a number of years, for 30 years now, but I would argue actually that that’s a good thing for physics. The word ‘crisis’ has a very different meaning in science, in particular in physics, than it has in other fields, in economy and so on because it is precisely when there are crises that new opportunities arise and there’s room for big breakthroughs. I’m personally quite optimistic that we’re going to learn much more on the nature of dark matter in the next decade because we’re going to have a lot of new information and new experimental efforts that will provide complimentary information about the nature of dark matter.

Host: Benjamin Thompson

That was Gianfranco Bertone from the University of Amsterdam talking to Lizzie Gibney. Gianfranco recently co-wrote a Review about the search for dark matter which you can find over at nature.com/nature.

Host: Charlotte Stoddart

Later in the show we’ll be talking about a new kind of implant that’s helping patients to walk again after spinal injury. That’s in the News Chat. Before then, Anna Nagle is here with this week’s Research Highlights.

[Jingle]

Interviewer: Anna Nagle

I’m sure you’ve always been dying to know what happens if you throw 200,000 dead salmon into a forest. Well, you’re in luck because now we’ve got an answer. For decades, researchers kept track of how many salmon were being eaten by bears in an Alaskan stream. They’d scoop the dead fish out of the water, count them, and then chuck the carcasses into the nearby forest to make sure they didn’t double count. But from 1997, they only lobbed the salmon onto the left-hand bank of the stream, meaning the trees on that side got a hefty dose of fishy fertiliser. Research revealed that these trees contained higher levels of a particular form of nitrogen usually found in marine ecosystems, and that they experienced a growth spurt dating from the start of the scientists’ salmon-slinging shenanigans. You can read more on that research in the journal Ecology.

[Jingle]

Interviewer: Anna Nagle

Space travel is known to put all kinds of stress on the human body, but what does a spell in space do to the brain’s volume? To find out, researchers from the University of Antwerp used MRI scans to look at the brains of ten Russian cosmonauts, once before a stint in orbit and twice after they’d returned to Earth. They found that after a period in space, some regions of the cosmonauts’ grey matter shrank, but recovered to pre-flight levels once they’d been back on Earth for around seven months. In contrast, the levels of cerebrospinal fluid – which cushions and cleanses the brain – had increased in certain regions after time in space and were still elevated many months later. The researchers say their findings may help explain some of the medical problems related to long-term space travel, and could help in planning future space missions. Float on over to the New England Journal of Medicine to find out more.

[Jingle]

Host: Charlotte Stoddart

Next up, Noah Baker has been exploring a difficult subject – suicide – and learning how the tech in our pockets might be able to help.

Interviewee: Matthew Nock

Some people get really quiet, you know, whenever you talk about death or mortality. People like at funerals tend to have, some people tend to shy away and not want to say anything more, but I would say the majority of people become interested when I mention that we’re doing this work to try and better understand suicide because most people have been touched by suicide in some way.

Interviewer: Noah Baker

This is Matthew Nock from Harvard University. He’s a psychologist who’s trying to understand, monitor, and prevent suicide using smartphones.

Interviewee: Matthew Nock

Suicide has been a leading cause of death for thousands of years, and the suicide rate in the US is virtually identical to what it was 100 years ago. I think there’s a lot of issues – ethical and legal and clinical – to work out but we can’t be paralysed by them because we have to do something. People are continuing to die and if we have technology that we think can do a better job, it is our responsibility to test it out and to take steps forward to try and improve the care that we can provide to people at risk.

Interviewer: Noah Baker

Over ten years ago, Matthew started his first study into suicide using tech.

Interviewee: Matthew Nock

So, the first study that we did in my lab was before smartphones were widely available. We outfitted self-injurious and suicidal adolescents with PalmPilots.

Interviewer: Noah Baker

Fast-forward ten years and Matthew has more options.

Interviewee: Matthew Nock

We’ve gone from being able to give people PalmPilots to having them wear harnesses under their clothes to measure things like heart rate and skin conductance to now just giving people a wrist-worn watch and loading an app on their smartphone, which most people have now anyway. So this work’s become much more feasible as these tools have become much more ubiquitous, and so it allows us to take bigger steps forward much more quickly.

Interviewer: Noah Baker

The people involved in Matthew’s experiments are all acutely suicidal, and they all give their consent to have apps loaded onto their smartphones.

Interviewee: Matthew Nock

These apps ping people several times a day to ask them about their thoughts and feelings and behaviours, including thoughts of suicide and intentions to act on those thoughts. Those are what we call the active data or the self-report data. In the background though, with their consent, we’re collecting data from their phone to see how active are they physically, how much are they moving around, where are they going, how long are they staying there, and what are they doing on their phone? Are they calling others, are people calling them, are they texting others, are people texting them? To get a sense of people’s social and physical activity and their sleep as well. And we also have them wear wrist-worn biosensors where we collect data also on their physical activity but also on their physiological arousal.

Interviewer: Noah Baker

The goal is to take all of these data and try to predict when someone might enter a suicidal state.

Interviewee: Matthew Nock

So far, we have one paper that we’ve finished that is not yet published, so I don’t want to say too much about the details of it, but we’re finding that using data from a person’s wrist-worn biosensor, we can predict with about 75% accuracy whether that person’s going to have serious thoughts of suicide the next day.

Interviewer: Noah Baker

The strongest indicators Matthew has found are things like lots of agitation and movement the night before an event.

Interviewee: Matthew Nock

And this is consistent with what we’ve heard for decades from clinician reports, that people who are suicidal before they make a suicide attempt or die by suicide have these periods of extreme unrest or agitation, a feeling of great psychological discomfort that might be in part driving their suicidal behaviour.

Interviewer: Noah Baker

Now, there are various caveats to these results, which we’ll get to in a minute. But before we do, it’s worth noting that the kind of forecasting Matthew describes would mean researchers could very well be finding out about a person’s emotional state before they’re even aware it’s coming. If that state could be sensed, Matthew then thinks that tried and tested psychological interventions – albeit a bit modified – could be beamed directly to the patient at the opportune moment.

Interviewee: Matthew Nock

We as a field of psychological science have made great strides in understanding how to use cognitive and behavioural approaches to decrease people’s depression and anxiety and psychological distress. What we’re doing is taking the same kind of skills, breaking them down into small pieces, and sending them to people exactly when we believe they’re in distress so they can use them when most needed.

Interviewer: Noah Baker

Now, I mentioned the caveats and here are a few of them. This only a small study – a few dozen people – and it’s yet to be seen if it will be repeatable across others or larger groups. And then there’s the problem of false positives. It’s important not to miss a potential suicidal event but predicting them too often could be just as dangerous.

Interviewee: Matthew Nock

If we are going to be beaming people interventions, we want to make sure we’re doing it at the right time, in the right place, and not having too many false positives because we don’t want to over-burden people or by sending interventions to them so much we could potentially reduce the potency of the intervention. So, we don’t want to be crying wolf, so to speak, and saying that many, many more people are at risk than really are.

Interviewer: Noah Baker

It’s also hard to ignore that a system which accurately predicts someone’s mood could have other more sinister uses outside of medicine.

Interviewee: Matthew Nock

Is there a possibility of misuse? If we know that someone’s in a period of emotional vulnerability, so to speak, does this open them up to be more likely to purchase certain kinds of care, certain kinds of interventions? I think that’s absolutely a possibility – not something that we’re doing but I think something we need to be mindful of so that we can ensure that people who are in a state of emotional distress of emotional vulnerability, so to speak, are provided with better care but not taken advantage of.

Host: Charlotte Stoddart

That was Matthew Nock from Harvard University speaking with Noah Baker. You can read more about Matthew’s work, and that of others in the field, in a Feature article at nature.com/news. If you’re affected by the issues discussed in this story, you can find a list of organisations that offer advice and support at go.nature.com/wellbeing. Click on the ‘support’ tab for that list.