Decoding our inner voice, and hunting for life on Mars
In this edition of The Naked Scientists: the scientists who think they can decode the thoughts we hear in our heads. Also ahead: do ultra-processed foods make it much harder to lose weight? Plus, we hear from the PhD student who is aiding the search for life on Mars...
In this episode
00:53 - Scientists decode the signals behind our thoughts
Scientists decode the signals behind our thoughts
Erin Kunz, Stanford University
Scientists at Stanford say they’ve decoded the brain signals behind our inner voice - the thoughts we hear in our heads - with around 74% accuracy. The breakthrough could let people who can’t speak communicate by simply thinking of a chosen word that’s turned into speech. Erin Kunz at Stanford University led the study...
Erin - Working with our participants in the previous studies, in which participants attempt to speak but they have a limited ability to do so due to, for example, ALS or stroke, we wanted to investigate a way that might be more comfortable or easier, so perhaps by imagining speaking instead of actually trying to speak, so bypassing the need for physical effort. The second motivation was that now as these systems are achieving impressive accuracies at decoding pretty much open-ended speech, we wanted to explore the possibility of these systems decoding something, words that the user may have not intended to be said aloud.
Chris - So is this almost like when we talk to ourselves, it's that inner voice you're seeking to pick up and decode and turn into an output?
Erin - Sort of. So we first were explicitly asking our participants to imagine aspects of them saying those words, so actually imagining the movement of their mouth or, for example, imagining the sound of their voice when they try to say the words.
Chris - And how were you recording the activity? Because this is picking up on brain activity, isn't it?
Erin - Yes, so we're recording from the motor cortex, so this is the part of the brain that controls basically our voluntary movement, so when you want to move your hand or when you want to speak, and specifically we're in the speech motor cortex, so focusing in on those areas that control your mouth and your tongue. And we're doing this with devices called micro-electrode arrays. They're about 3.4 millimetres square, so smaller than a pea, and these are placed on the cortex during a surgery. And these have 64 electrodes on them, things that record the electrical signals of individual neurons firing in the brain. We can record those signals in real time for this study.
Chris - There must be a long training phase then, so presumably you instruct your participant to think about this word or this sound, and you must work your way almost like through a dictionary of different signature sounds or speech outputs so that you can work out what the different neurological patterns are that would correspond to each of those.
Erin - Yeah, that's correct. So we cue participants with sentences on a screen, so for example, the sentence, I feel good. So the participant will see that sentence and then they'll imagine saying that sentence, and then we do several of these sentences. So in the study, depending on the participant, they imagined between 80 and 500 of these sentences in order to train the models to decode the patterns of their speech that were associated with individual phonemes, individual speech units, basically. In the English language, we have 39 phonemes, and those are what make up the words. And so then the decoder can take that sequence of phonemes and identify what the most likely words were from them.
Chris - And then what do you do, flip it round? So you say, well, now it's learned what the brain does when we tell it to imagine saying X. Now we flip it round, we look at what it's saying it thinks the person said and ask them, is that what you really wanted to say?
Erin - Yes, that's correct. So once the decoders are trained to identify those patterns, then the participants can imagine saying what they want, and the decoder can decode that.
Chris - And how accurate is it when you then start just looking at the activity that's coming out and then asking the person, is that what you were thinking of? How right is it?
Erin - So it varied across participants, but in the best case scenario, we were able to get an 86% accuracy when decoding from 50 words and a 74% accuracy when decoding from a large vocabulary of 125,000 words, which would essentially be being able to say anything you want.
Chris - Well, when one thinks about how many mistakes we make with fat thumbs trying to type text messages, that's pretty good.
Erin - Yeah, it's pretty good. And also for reference, systems like Siri or Alexa typically get around a 95% accuracy. So that's generally thought of being the sort of transition point between usable and not usable.
Chris - Can it continue to learn though? Because obviously everyone's a bit different, and it must be possible to pick up on foibles of how people think or tune it slightly more with time. So can it continue to learn? So will performance potentially continue to rise in these people, or is it topping out at that roughly 75, 80% accuracy?
Erin - Yes, absolutely. So this was an initial proof of concept. So we have pretty limited amounts of training data. And since this study was completed, we've continued to collect some training data. So we're still exploring the possibility of achieving higher accuracies with this type of device.
Chris - And crucially, in the people with disabilities whom this could be applied to, where existing systems are quite fatiguing to use, trying to blink or look at things or breathe to move cursors around, is this a lot less cognitively taxing for these people? So they find that communication is much more effortless?
Erin - I think some participants report that it is less effortful. Some participants don't mind as much when they're attempting to speak. So I think it's just offering another option, depending on user preferences.
Chris - And what did the end users make of it?
Erin - I think there was excitement about the possibility of this both being less effortful, as well as the potential for it to reach faster communication rates. Even though the systems like this that are built on using attempted speak are quite a bit faster than some of the previous options available, they're still not quite at the speed of typical conversation. I think the fastest study published has reached about 90 words per minute, whereas typical conversational speech is close to 150 words per minute. So this sort of inner speech decoding may be a way to reach those conversational rates of speech. And notably, at least a few of our participants have expressed the enthusiasm about the ability to potentially interrupt a conversation.
Chris - Now, given that what you've effectively got here is a system that can hear a person's thoughts inside their head potentially, that there might be things they say and they didn't actually want the computer to hear it. Is there an ethical angle to this as well? And were any of your participants or anybody in the study uncomfortable about the fact that you're now probing something that previously would be completely private to a person?
Erin - So yes, we wanted to responsibly address this question. And I will point out that we've also looked into comparing the sort of inner speech representation to attempted speech and that there is strong distinguishability between those two. And we've actually proposed two methods in the paper for addressing this in ways that the system can either totally ignore inner speech altogether if someone's using a system based on attempted speech, or else a password that will allow the user to control when the decoder is running. So you can sort of think of that as saying, hey, Siri, or hey, Alexa. And if it doesn't receive that command first, it just ignores.
Chris - So there's like a wake word for the interface. So the person can divorce themselves from having their thoughts read when they want a private moment.
Erin - Yes.
08:47 - Ultra-processed foods make it harder to lose weight
Ultra-processed foods make it harder to lose weight
Sam Dicken, University College London
Obesity researchers in London have found that eating ultra processed foods makes it harder to lose weight. These foods are manufactured for convenience, and often contain high levels of sugar and unsaturated fats. But a new study - which has been published in Nature Medicine - found that a diet of less processed food may be more beneficial for weight loss. Here’s Sam Dicken at University College London…
Sam - So we've seen growing evidence around higher intakes of ultra-processed foods. So these are foods that are made with the purpose of being highly profitable, so they're very cheap, accessible and tasty and want you coming back for more. Typically, these foods are very nutritionally poor, but actually some of these ultra-processed foods are nutritionally better. And no one's actually looked yet at whether ultra-processed foods that meet our current dietary guidance can be healthy. So we put that to the test.
Chris - How did you test it?
Sam - The best way to test diets and interventions is to do a clinical trial. So we gave participants a healthy balanced diet based on the current NHS guidance, that's having your five portions of fruit and veg a day, not eating too many foods high in saturated fat, sugar and salt, and having the recommended fibre intakes. We provided these diets, one ultra-processed one minimally processed. These are the kinds of meals that you make from scratch at home with raw ingredients. And they were provided for free, delivered twice a week to participants' homes. We removed all these barriers that people face when accessing a healthy diet. So we provide it for free, ready prepared and with a menu guide. And what we wanted participants to do was to have as much or as little as they wanted of these diets. Because we think ultra-processed foods get people to eat more than they need. So we're going to test that in the context of the current dietary guidance.
Chris - Were the people trying to lose weight or gain weight? What was their health status before you started on this trial?
Sam - So our participants were living with being overweight or obese. So that's the body mass index between 25 and 40 kilograms per metre squared. So it's your weight divided by your height squared. And the average person in the UK has a BMI of around 26 to 27. And participants were not told that the trial we're looking at weight as the primary outcome, our main outcome of interest. And participants were not told to restrict their intake. We provided more energy than they needed in abundance of these two healthy balanced diets. And they were just told to eat as much or as little as they wanted until they felt satisfied and full.
Chris - So basically, you're presenting these people for one period of time with a really wholesome, healthy diet made from minimally processed foods that they would want to eat. And then the rest of the trial, you're doing the same thing, but with ultra-processed ingredients. And the outcome measure is does their weight change?
Sam - Exactly that. So the one diet minimally processed, the kind of food you think of is to be healthy. And the ultra-processed diet might be high fibre breakfast cereals, nutritionally improved sandwiches and meal deals, ready meals and snack bars, but all meeting our current guidance.
Chris - So what happened then? Did you see a difference?
Sam - Really interestingly, we saw that on both diets, people ate less than they were before they started the trial. Most probably because the diets they were eating before weren't aligned with our current dietary guidance. They were eating too much saturated fat, sugar and salt, and not enough fruit and veg. These nutritionally improved diets, whether ultra-processed or minimally processed, resulted in significant weight loss. What's really interesting is when participants had the minimally processed diet, they lost twice as much weight, significantly more weight loss than the ultra-processed diet.
Chris - This is really interesting. So ultra-processed foods are not necessarily awful then, they can, in the right hands and mouths, translate into a loss of weight, but they're still not as good as if you make food from scratch. I mean, that's the take-home from this then.
Sam - It is indeed. And a good way to think about this is, not all ultra-processed foods are intrinsically unhealthy, but there's an effect. When that food has had the purpose of being made to be highly profitable, tasty, cheap and accessible, we tend to see that there's an effect on how much we eat and weight change compared to the same food if it wasn't going through this same process.
Chris - Did the participants eat roughly the same amounts on both diets or did they lose more weight on the minimally processed foods because they ate less of it, because actually they enjoyed it less?
Sam - There were two ways we estimated their energy intakes on the trial. We asked them through dietary reports, which can sometimes be a bit inaccurate because people tend to under-report. The other way is that we based it on the amount of change in their muscle mass and fat mass that changed across the diets. And we saw that there was a significant reduction in their energy intake on the ultra-processed diet from baseline, but a significantly greater reduction in their energy intake on the minimally processed diet compared to baseline and the ultra-processed diet.
Chris - What's the take home from this then, as opposed to take away? I suppose you could say, we've got a population of the world actually that are overweight and obese at extreme levels now, and we're trying to combat this. What does this study add? What should people do differently?
Sam - We know that the biggest barriers to accessing healthy food is cost. In the UK, the lowest 20% of people in terms of income have to spend 70% of their disposable income to meet our current dietary guidance, compared to 10% of the highest 20% of income. And that was reported in the Food Foundation Broken Plate Report earlier this year. So what we need to do is clearly our current dietary guidance works, but it seems to be more favorable. We get greater weight loss and other aspects when it's a minimally processed diet. So we need high level action from governments to change the financial drivers that dominate our food supply. And rather than just being purely driven by profit, also have health and the environment as stakeholders. So we're developing foods that are incentivized to improve our health and not just our back pockets.
Chris - So at the moment, someone who goes into a convenience store and they're hungry because it's the end of the day, they've got a family to feed, they're in a hurry, they're going to reach for the ultra-processed ready meals and so on, because that's the easy option. It's also often the cheaper option. If we can flip that round, you're saying, and this study kind of suggests that we're eating more minimally processed ingredients and making more meals from scratch, which are at the moment more expensive. So if we could make them cheaper, and therefore there would be a price incentive to consume them more, you're arguing that would be a double win, because we would be healthier, and the weight loss that people would achieve, or at least not gaining as much weight would be greater.
Sam - Indeed, it seems to be a more cost effective approach to improving diets. And globally, we see that it's a lack of healthy food. So fruits, vegetables, whole grains, fibre, that's linked with early mortality and greater disease, and the more so than unhealthy components, we really need to think about how we're improving access to healthy foods, but not by individuals, by systems and governments and communities.
16:32 - Sensors on Mars Rover could be tweaked to hunt for life
Sensors on Mars Rover could be tweaked to hunt for life
Solomon Hirsch, Imperial College London
A PhD student at Imperial College London says he's found a way to use existing scientific tools to search for active life on Mars. Solomon Hirsch says the discovery could avoid the need for costly new missions to the Red Planet. I've been speaking with him...
Solomon - Well, the work we have here is some work we did on the equipment in our lab that closely replicates the equipment that is used on the surface of Mars. And we found that this equipment is able to distinguish between living and dead things, basically. So we've not found any evidence of life yet. But if we do, one of the first questions is, is it living now or is it dead? And hopefully the signals that we've detected in these experiments will help us answer that question in the future.
Chris - Had the people who built the analytical instruments on the rovers not realised that this was what they could do then?
Solomon - I have read previous mission statements that have said that this ability is lacking. And it comes with some limitations. The main one being that we don't know what life is going to be like beyond Earth. We're really making the massive assumption here that it's similar to Earth. It's the best assumption we have. You know, we might think things might have evolved in similar ways on other planets. So we're not saying this is 100% perfect test for all life. But with the best information we've got and using the equipment that we know that works, I think, yeah, we have discovered a new way that this equipment can be used.
Chris - What is the signal that you think you can look for then?
Solomon - We started by looking at these molecules that are found in the membranes of most cells on Earth. So if these molecules aren't there, the membrane can't form and the cell will die. And when a cell dies, these membranes break down very quickly, mainly because they're eaten by other things. So these are a really good marker of living things because they break down really quickly when something's dead. So if they're there, then we expect that something is alive. We took these compounds and put them through our system and tried to see whether there was any distinctive signal of these compounds compared to the compounds that you get after something's died. And we found a few particular compounds that could distinguish that these compounds that are indicative of living things.
Chris - What are the chemicals?
Solomon - They're called intact polar lipids, and they are long chains of carbon. One end is positively charged and the other end is negatively charged. And that kind of charge distribution causes these quite large molecules to arrange themselves into a membrane. A lot of them contain phosphate or phosphorus, not all of them. And in fact, our signal doesn't rely on the phosphorus. It just relies on the kind of most standard arrangement of these compounds.
Chris - And how do you see them? As in what instrument on the rovers and what instrument in your lab enables you to see them? And with what sort of sensitivity?
Solomon - Very good question. It's something called a GCMS, which is gas chromatography mass spectrometry. Very long winded. When I first used it, it just seemed like a magic machine. You put something in and it tells you what it is. I couldn't believe it existed. It works very well for organic chemicals, especially because life is based on organic chemicals, one of the main targets for astrobiology. The mass spectrometer part is probably the most intuitive to understand. We're trying to find the mass of the molecule basically. And then from that, we can figure out what the compound is.
Chris - And rovers like Curiosity have got these devices aboard and therefore could go looking for these compounds that you say are indicative of a life process, because if they break down so quickly, if they're there, something must be actively making them.
Solomon - Exactly. Yeah. It's been used many times before. The Viking landers had this GCMS equipment. Curiosity had it. The ExoMars, the mission that's launching in a few years time will have it as well. The Dragonfly mission, Titan will also have it. So it's well tested in space and we know it can work in those environments.
Chris - And the sensitivity?
Solomon - We know this equipment works. We know this signal should be there if something is living. And the sensitivity should be high. We need to do more work to specifically give you a number on that sensitivity. But this equipment has been used at very high sensitivities. And you can even tune the equipment. Now we know what we're looking for, you can tune it to give you a high sensitivity if you know what you're looking for.
Chris - Have you spoken to the mission teams to see if you can get this integrated into the experiments and just start sniffing around to see what's there?
Solomon - If you find some evidence of biology somewhere else in the solar system, I think, to my mind, that's just immediately. Is it living now or is it dead? So it will become useful once we kind of reach that threshold of, okay, this looks like a biological signal. Now can we tell whether it's living or dead?
21:32 - How butterfly wings could revolutionise solar panels
How butterfly wings could revolutionise solar panels
Katie Shanks, University of Exeter & Sophie Gledhill, Fraunhofer-Institut für Solare Energiesysteme ISE
In the hunt for sustainable energy, solar power has emerged as a front runner for supplying part of the world’s energy needs. And Will Tingle has been finding out how three species of butterfly have the potential to make them an even more attractive source of power, in every sense of the word…
Will - There can be no doubt that solar panels offer a cheap and decentralised way of generating energy, but there are always improvements to be made when it comes to getting the most power out of each panel. That's where our first two butterflies come into play. The more light you can get to hit a panel, the more energy you can produce. Thanks to work supported by UK Research and Innovation, we can take inspiration from nature to channel more light towards these solar modules. To find out more, I've been speaking with the University of Exeter's Katie Shanks.
Katie - When we think about nature, it's probably the ultimate trial and error. We wanted to make very lightweight optics, and butterfly wings do that perfectly.
Will - And was there a particular species that you focused on?
Katie - So I started looking at the cabbage white butterfly, which has very lightweight reflective wings. And then I also started looking at the glasswing butterfly, which has opposite properties. So it's very transparent, very anti-reflective. And so in that way, I had two blueprints to help understand and develop our own optics for solar panels.
Will - So I think I see what you're getting at with the glasswing butterflies. Obviously, as the name suggests, they have these translucent wings. And if you're saying that they can absorb light very well, that sounds pretty useful if you're a solar panel. But why did you go for cabbage white?
Katie - The cabbage white actually does this very interesting behavior in the morning, where it sunbathes with its wings in a V-shape. And the V-shape of the cabbage white's wings helps focus light onto its body, onto its flight muscles, so it can fly quicker than other butterflies would. And so if you're increasing the amount of energy, the amount of sunlight into your solar panel, you're increasing the amount of energy out without actually having to increase the solar panel material you're using.
Will - So it's the idea then that you can have kind of the best of both worlds there. If you have an outer sort of shape of this cabbage white reflecting the light in, and then this glasswing butterfly structure on the solar panel itself, you've got this almost hyper concentration of light hitting the solar panel.
Katie - Exactly.
Will - Obviously, the butterflies themselves produce these structures with very specialised proteins in their wings that create certain shapes that can refract or reflect the light as they desire. That's probably not an option to use. So what materials are you using to try and replicate these effects?
Katie - We're looking at, for example, for the cabbage white butterfly, titanium dioxide material. For the glasswing butterfly, we're actually, I'm working with the collaborators at Pittsburgh University who can actually etch these structures into glass.
Will - Is this something you could apply to already created solar panels, or does this have to be a fresh new solar panel that needs producing?
Katie - So that's a good question. So applying it to current solar panels is feasible. I guess the question would be, would you be uninstalling and installing a solar panel? And it would come down to how old that solar panel was and if it was worthwhile also upgrading the solar cell technology as well.
Will - Do you foresee this being something that could be rolled out worldwide? Is it versatile? Is it durable enough, do you think?
Katie - So one of the interesting properties of these nanostructures, the glasswing nanostructures, is that they also have properties such as hydrophobic. So whenever water hits them, whenever rain hits them, it rolls off easily. In terms of durability, they shouldn't be any less durable than current solar panels.
And in terms of rollout and scalability, we've already analysed how this technology will perform in different areas of the world. So solar panels on a wall or installed vertically near the equator, where the sun is very high in the sky, we see about a 15% increase in energy output throughout the year. And in the same extreme condition of, say, a horizontal panel, but closer to the north or the south poles, again, we have close to the 15% increase. So it's kind of those non-ideal installations, which we'll be seeing more of as we install more solar panels. And for vehicles as well, that's where there's the biggest impact and where we think there's going to be a lot of demand.
Will - Katie Shanks. So that's how butterflies are giving solar input a boost. But there is another facet of solar cells that is also worth considering. If they are to become an increasing presence in our lives, do they have to look like a big black square? Well, perhaps not. You may be familiar with the blue morpho butterfly. If not in name, then by the fact that it's the giant blue butterfly that signifies you're in the tropics in most forms of media. But did you know that that blue isn't a pigment? Instead, it's the result of light hitting scales on the butterfly's wings. These scales interfere with the light and only reflect the blue wavelengths of light. Well, if you could harness that structure on the wings as a kind of a window pane and slide it on top of a solar cell, well, you could turn them blue, or it turns out pretty much any other colour you want, as I've been hearing from Fraunhofer Institute for Solar Energy Systems, Sophie Gledhill.
Sophie - What we've done in the Fraunhofer Institute for Solar Energy Systems is develop a technology which we call the morpho colour. And this technology allows the solar modules to have a designed colour, working on the similar principles as the morpho butterflies. So we deposit these thin multi-layer films of alternating high and low refractive indexes on either microstructured glass or a microstructured polyester based film. You either laminate your microstructured glass with your multi-layered films into your module, or alternatively, if it's on a flexible film, you can also laminate that in between the glass and the module. And so it's very compatible with any standard solar technology and any module manufacturers can produce this technology in a range of colours and forms as they so desire.
Will - I'm imagining the skyscrapers of the future coming with these solar panels on them.
Sophie - Yes, so skyscrapers or heritage buildings, where you have to blend your material, your solar panels into the original building materials, say making terracotta solar modules. The morpho colour technology, which is what we produce at the Fraunhofer Institute for Solar Energy, has been licensed to a Swiss module construction company, Megasol. And they've announced a really cool new project to construct a massive rainbow solar module display in the pride flag colours so that you have a strip of red, a strip of orange modules, yellow, green, blue and violet on one side of the roof in the St. Pauli football stadium in Hamburg.
Will - Crucially, I guess, the bog standard solar panel, as I understand it, is made black by default because that absorbs the most light. Is this going to decrease the amount of light that can go into that solar panel?
Sophie - So of course, for the colour to be perceived by the eye, there is also some reflection in the specific wavelengths. For example, the green solar cell, you need to reflect in the green wavelengths, but you would reflect back with a very low amplitude and a very narrow bandwidth. And this corresponds to a marginal loss in the light energy in these wavelengths. However, for a green solar module with the morpho colour coating, that yields about 95% of the efficiency of compared to a standard black module. And we have this marginal loss in reflectance with the specified colour.
Will - Sophie Gledhill. So with the power of three butterflies combined, more efficient and more vibrant solar panels could be coming soon to a town near you.
Katie's work was carried out with the support of UK Research and Innovation.
29:58 - How similar do two animals have to be to have babies?
How similar do two animals have to be to have babies?
Thanks for sending that one in, Girts!
Domestic dogs - Canis lupus familiaris - may appear quite different from breed to breed, but are all in fact the same species. Provided they can, anatomically speaking, do the business, 2 dogs should be able to produce viable offspring.
Foxes belong to the same family as dogs - canidae - but a different genus: vulpes. As a general rule, animals who don’t belong to the same species aren’t compatible parents. But why is this? I’ve been speaking to Gary England, Professor of Comparative Veterinary Reproduction at the University of Nottingham…
Gary - So could there be a dog-fox hybrid? And the significant factor in whether they could reproduce will be around their chromosome number. So the number of chromosomes must align well enough so that when the egg and the sperm come together, a viable embryo can form.
James - Chromosomes contain all of the genetic material - the DNA - that's required to code for the development, growth, function and reproduction of an animal. They come in pairs: dogs have 39 pairs of chromosomes, totalling 78.
Gary - If you think about the biology of fertilisation, obviously we have to get some chromosomes from the female and some chromosomes from the male. So what has to happen is during the process of formation of the sperm and of the egg, the chromosome number has to halve. And that's a process called meiosis. Each of those offspring cells contains half of the number of chromosomes. So it contains one of the pairs of chromosomes. So when the egg and the sperm then join together, when fertilisation occurs and the embryo forms, those chromosome pairs can come back together, half of them from the sperm, half of them from the egg. And so we end up again with 39 pairs of chromosomes or 78 chromosomes in total.
James - This is what leads to the development of a successful embryo between mating dogs. But what about foxes?
Gary - If we assume that the question is about the red fox, the typical fox, the European fox, that is in the different genus. It's in the genus of vulpes. There's actually 12 species of fox altogether. The fox has only got 17 pairs of chromosomes. So the 17 pairs of chromosomes obviously doesn't match very well with the 39 pairs of chromosomes that we see in the domestic dog. So if we tried to have a red fox hybrid, we've got a big mismatch in the chromosome number. So it's very unlikely that the chromosomes will pair up and form a viable embryo.
James - So Girts, for two animals to produce offspring, they need to have a compatible number of chromosomes so that they align during fertilsation. Because chromosome numbers vary greatly between species, often even when they belong to the same family taxonomically speaking, you won’t get viable embryos in most cases of cross species copulation.
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