Today there are over eight billion people on Earth. That?s an awe-inspiring figure? but how does it compare to the vast numbers who came before us? Listener Alpha wants to know how many people have ever existed, so CrowdScience sets out to do a historical headcount.

The Population Reference Bureau in the USA estimated this number back in the 90s, and have been updating their calculations ever since. Demographer Toshiko Kaneda explains how their model works, the assumptions it makes ? and the huge uncertainties around the number it comes out with.

We first need a date for when ?humans? first began, so Caroline travels to the Natural History Museum in London to meet human evolution expert Chris Stringer, and marvel at his collection of replica fossil skulls. Chris demonstrates how to distinguish our species, Homo sapiens, from other species like Neanderthals. When did these species first appear - and which of them count as human?

And once you know where to start the clock, how do you estimate the numbers of people alive at different points in history? For a population demographer like Walter Scheidel, it helps that some ancient civilisations kept detailed censuses, a few of which have survived to the present day. Caroline and Walter pour over one of these census fragments, and learn how to combine them with other archaeological clues to get some very rough numbers.

And finally: what does the future of our population look like? Poonam Muttreja from the Population Foundation of India discusses developments in the world?s most populous country, as well as the big demographic trends ahead for humanity.

Presenter: Caroline Steel Producer: Phil Sansom Additional Recording: Umaru Fofana Editor: Cathy Edwards Production Co-ordinator: Connor Morgans Studio Manager: Sue Maillot

Featuring: Toshiko Kaneda, Technical Director of Demographic Research, Population Reference Bureau Chris Stringer, Research Leader in Human Evolution, Natural History Museum London Walter Scheidel, Professor of Classics and History, Stanford University Poonam Muttreja, Executive Director, Population Foundation of India

We spend a lot of our time thinking about climate change, but listener Paul has a question that isn?t usually part of the conversation. He wants to know whether a hotter atmosphere will affect how often volcanoes erupt, or make them more explosive when they do.

CrowdScience travels to New Zealand to search for answers, exploring volcanic craters and discovering traditional Maori knowledge about volcanoes.

Contributors: Geoff Kilgour, Volcanologist, Geological and Nuclear Sciences Taupo, New Zealand Heather Handley, Volcanologist, University of Twente, The Netherlands Pouroto Ngaropo, Historian and Matauranga M?ori expert, Rotorua, New Zealand

Presenter: Caroline Steel Producer: Emily Bird Editor: Cathy Edwards Production Co-Ordinator: Connor Morgans Sound Engineer: Steve Greenwood

(Photo: Icelandic volcano. Credit: KRISTINN MAGNUSSON/Getty Images)

Many of us have habits that calm us down in times of stress. Things we find deeply comforting, like sucking our thumb or biting our nails. We might not even be aware we?re doing them, but they play a fundamental role in helping us regulate our emotions.

Our question this week comes from CrowdScience listener and nail-biter, Ash. He wants to know where these habits come from. And since his pet dog is also a nail-biter: do we share these traits with other animals?

Recently, a video of a mouse cleaning up a man?s shed took the internet by storm. Was this a house-proud mouse, or was it the animal's way of making sense of a frenetic environment? An emerging field of scientists focusing on animal behaviour and emotions help us shed some light on such questions.

Along the way we meet a dog training specialist, learn what a sniffari is, go for playtime with a thumb-sucking otter, and visit an OCD clinic. We?ll also be getting tips on how to give your pets the best home environment, and meet an animal enrichment officer in South Africa, who knows how to spot the signs of an unhelpful habit developing.

Contributors: Karolina Westlund, Ethologist, Stockholm University and ILLIS Ben Terry, CBT Therapist, Priory Hospital North London Karin Pienaar, Animal Behaviourist, COAPE International Candice Ward, Animal Behaviourist, Johannesburg Zoo

Jaak Panksepp clip: The science of emotions: Jaak Panksepp at TEDxRainier

Producer: Robbie Wojciechowski Presenter: Alex Lathbridge Editor: Cathy Edwards Production co-ordinator: Connor Morgans Additional recording by Elna Schutz

(Photo: Portrait of border collie puppy biting a curtain. Credit: Rawlstock/Getty Images)

Crowd Science listener Maik wants to know what the BMI is and what his BMI score says about his body. He trains dogs for a living and wonders if, like different breeds of dog, we simply have different body types? Marnie Chesterton comes up with some answers, talking to doctors about how the BMI is used and misused in clinical practice, and looks at some alternative methods for measuring our body composition. She also sits down with philosopher Kate Manne to discuss the realities of living in a fat-phobic world. We hear from Tonga in the South Pacific, where high BMI scores have labelled the country highly obese. But this is not necessarily how Tongans see themselves. And Marnie finds out if the BMI will continue to be used across the world as an important health marker or whether it is destined for the scrap heap of medical history. Contributors: Professor Kate Manne Dr Francesco Rubino Dr Naveed Sattar Professor Brendon Noble Technician Leah Siegel Fononga Pulu Sela Latailakepa Presenter: Marnie Chesterton Producer: Richard Walker Editor: Cathy Edwards Production co-ordinator: Connor Morgans Studio manager: Emma Harth

CrowdScience listener Gregory wants to know what affects the way we see the colours of the world. He was looking at a blue summer sky with a friend and they got to wondering whether they both see the same colour blue. So what does influence our vision of the colours that surround us? Could eye colour have anything to do with it? And can we ever really know if your blue sky is the same as mine?

Caroline Steel comes up with some answers, talking to colour scientists about their research into the multiple factors that enable us to see in multi colours, from the intricate biology of our eye to the changing environment around us.

She also investigates her own colour vision and solves a personal mystery, discovering why the world has always looked a slightly different colour from each eye.

Contributors: Professor Jay Neitz, Department of Opthalmology, University of Washington, US Professor Hannah Smithson, Department of Experimental Psychology, University of Oxford Dr Juan Perea García, researcher, Department of Cognitive Psychology, University of Leiden Dr Lauren Welbourne, researcher, Department of Psychology, University of York Dr Adam Bibbey, lecturer in sport, Department of Sport, Oxford Brookes University

Presenter: Caroline Steel Producer: Jo Glanville Editor: Cathy Edwards Production co-ordinator: Connor Morgans Studio manager: Jackie Margerum

(Photo: LWA)

Storing your data in ?the cloud? might sound like an ethereal, intangible place, but it?s actually a physical location - a data centre. CrowdScience listener Art is worried about how much energy and water data centres are consuming. He?s from Ireland, where data centres are gobbling up almost 20% of the national electricity supply and that?s growing, fast.

So how much energy and water are data centres using globally? And how can they become more sustainable? To answer Art?s question CrowdScience heads to chilly western Norway to visit a data centre hidden deep within a mountain, that?s said to be one of the most efficient in the world. And we hear how a data centre in South Africa is saving water and dealing with crippling power cuts by generating its own renewable energy.

Do we just need to stream less TV and reduce our email inbox? With the help of carbon footprint expert Mike Berners-Lee, we crunch the numbers to find out.

Featuring: Svein Atle Hagaseth, CEO of Green Mountain data centres in Norway Mike Berners-Lee, Professor at Lancaster University?s Environment Centre and consultant at Small World Consulting Thulani Ncube, Group Energy Lead at Africa Data Centres

Presenter: Anand Jagatia Producer: Sophie Eastaugh Editor: Cathy Edwards Studio Manager: Donald MacDonald Production: Jonathan Harris & Connor Morgans Additional Recording by: Kobus van Niekerk

Why do humans have wisdom teeth if so many of them get removed soon after they appear?

Wisdom teeth, the third molars in the back of our mouths, are so called because they normally appear in late teenage, early adulthood ? the time in life we supposedly have learned some wisdom. But around 25% of people don?t develop all four. Of those that do emerge, it is not uncommon for them to appear at nasty angles, jutting into the tooth next door causing potentially dangerous infections and pain. Because of this, for decades many people have them surgically removed.

Listener Khaleel was preparing to have his remaining wisdom teeth removed when he wrote to CrowdScience to ask about them. Given that they can seem to cause more harm than good, why has evolution resulted in these troublesome teeth? But many people have perfectly uneventful relationships with their wisdom teeth, so have we perhaps removed more than we needed to over the years?

Anand Jagatia chews it over with the help of surgeons and dentists to try to extract the truth ? why DO we have wisdom teeth?

Featuring: Tanya M Smith, Professor in the Australian Research Centre for Human Evolution at Griffith University, Australia Patrick Magennis, Consultant Oral & Maxillofacial Surgeon at University Hospitals Aintree, Liverpool UK Verena Toedtling, Dentist and Specialist Oral Surgeon, UK

Presented by Anand Jagatia Produced by Alex Mansfield

When the first person set the very first clock, how did they know what time to set it to? This question, from listener Chris in the UK, sends CrowdScience off on a quest into the history of timekeeping.

From sundials to water clocks, from uneven hours to precision seconds determined by the vibration of an atom, we examine how we came to measure time. We visit possibly the oldest working mechanical clock in the world to discover how its time was originally set; and hear how the time we go by today is not quite the same as it was in the past.

Will all this be enough to solve Chris' question, or has he stumped the team?

Featuring:

Ian Westworth, Clock Mechanic Dr. Chad Orzel, Associate Professor of Physics and Astronomy at Union College Anna Rolls, Curator of Clocks, Clockmakers? Museum Peter, Guide, Salisbury Cathedral Dr. Jun Ye, Physicist at NIST (National Institutes of Standards and Technology) and The University of Colorado, Boulder.

Presenter: Caroline Steel Producer: Margaret Sessa-Hawkins Editor: Cathy Edwards Production Co-ordinator: Jonathan Harris Studio Manager: Jackie Margerum

(Photo:Stopwatch on red background. Credit: Martin Poole / Getty Images).

In 2011, CrowdScience listener Amanda survived the devastating earthquake in Christchurch, New Zealand.

It arrived unannounced - as all earthquakes do - leaving her with no time to prepare a response. So Amanda wants to know whether science will ever be able to give us advance warning of quakes.

To explore her question CrowdScience heads to New Zealand to meet listener Amanda, as well as the brains behind the country?s earthquake forecasting models. We dig in a field for thousand-year-old tectonic clues that could help us understand when the next earthquake might strike. But even if we could get a head start against a quake, would we respond in the right way?

Please note: earthquake response advice varies by location. Please check local guidance and individual building procedures.

Featuring:

Nicola Litchfield, Principal Scientist in Paleoseismology at GNS, Wellington, New Zealand Matt Gerstenberger, Seismologist and leader of the National Seismic Hazard Model, GNS, Wellington, New Zealand Andy Howell, University of Canterbury, New Zealand Lauren Vinnell, Lecturer in Emergency Management at the Joint Centre for Disaster Research at Massey University

Presenter: Caroline Steel Producer: Emily Bird Editor: Cathy Edwards Production: Jonathan Harris, Jana Holesworth Sound Engineer: Steve Greenwood

(Photo: Earthquake damage in Christchurch. Credit: John Crux Photography)

Have you ever been through a romantic break up, unable to shift the ex from your thoughts? You are, obviously, not alone?

Listener Elkin, experienced just that. But rather than wallowing in self-pity, he sought out an explanation. Where better to get it, than from CrowdScience. Now, Alex Lathbridge is putting on his thinking cap to find out why we daydream?

Presenter: Alex Lathbridge Producer: Harrison Lewis Editor: Martin Smith Production: Jonathan Harris

Featuring:

Giulia Poerio, Lecturer in Psychology, University of Sussex. Kalina Christoff, Professor of Psychology, University of British Columbia. Eli Sommer, Israeli Professor of Clinical Psychology, University of Haifa. Sophie Forster, Reader in Psychology, University of Sussex

(Photo: Man daydreaming surrounded by clouds. Credit: jacquesdurocher / Getty Images)

Presenter Marnie Chesterton and the team pit their wits against a multitude of mind-bending puzzles from an old TV gameshow - all in the name of answering a question from Antonia in Cyprus: how do we work out how clever someone is? Is IQ the best measure of cleverness? Why do we put such weight on academic performance? And where does emotional intelligence fit into it all?

In the search for answers Marnie and the team are locked in rooms to battle mental, physical, mystery and skill-based challenges, all against the clock.

Unpicking their efforts in the studio are a global team of cleverness researchers: Dr Stuart Ritchie from Kings College London, Prof Sophie von Stumm from York University and Dr Alex Burgoyne from Georgia Institute of Technology in the US.

They are challenged to face the toughest questions in their field: Why do men and women tend to perform differently in these tests? Is our smartness in our genes? And what about the Flynn Effect ? where IQs appear to have risen, decade after decade, around the world.

Producer/presenter: Marnie Chesterton Editor: Richard Collings Production co-ordinator: Jonathan Harris

(Photo Man doing puzzle. Credit: Getty Images)

What evidence is there for a semi-aquatic period in human evolutionary history? That?s the question that?s been bothering listener Dave in Thailand. He thinks our lack of hair and love of water might indicate that, at some point, we were more water-based than we are now. But what does science have to say on the matter?

The theory that our ape ancestors returned to the water for a phase in our evolutionary history is a controversial idea that most scientists disagree with.

Anand Jagatia chats to Dr Melissa Ilardo, assistant professor at the University of Utah, about our dive reflex - a physiological response we display when submerged underwater, which helps direct oxygen towards vital organs. But this is not a response that is unique to humans - it is found in all mammals. Experts say it developed long before all apes split off in the evolutionary tree.

To find out more about the theory itself Anand hears from John Langdon, emeritus professor at the University of Indianapolis. He explains why the aquatic ape theory is not generally accepted by anthropologists, what the fossil record can tell us about our evolutionary path and why evolution is much more complex than the aquatic ape hypothesis suggests.

While there may be little evidence of a semi-aquatic period in our evolutionary past, there are some communities around the world that have adapted to utilising their watery environments in more recent evolutionary history.

Anand speaks to Dr Nicole Smith-Guzman at the Smithsonian Tropical Research Institute who has found evidence that ancient populations in Panama were habitually diving in the sea for shells and seafood. She explains how she can piece together evidence from different sources to detect the activity of ancient populations. And Dr Melissa Ilardo explains how evolutionary pressure can cause physical changes in isolated communities, as our bodies ultimately adapt to help us thrive in more watery environments.

Producer: Hannah Fisher Presenter: Anand Jagatia Editor: Richard Collings Production co-ordinator: Jonathan Harris Sound engineer: Jackie Margerum

(Photo: Woman swimming underwater. Credit: Petrelos/Getty Images)

Our question this week comes from a father and his two young boys. They want to know whether it?s possible to plant enough trees to soak up all the extra carbon we are putting into the atmosphere? The quest to find answers takes us to a remote reforestation project in the Carpathian Mountains in Romania which could be a model for other projects looking to tackle the climate crisis through reforestation. We speak to experts to find out how much tree planting and reforestation can do in helping combat the climate crisis. Presenter: Caroline Steel Producer: Margaret Sessa-Hawkins Editor: Richard Collings

Noise pollution from vehicles in the public space has a huge impact on human health. But as the world switches to quieter electric-powered means of transport there?s a debate about whether we will actually see any noticeable improvement to our quality of life.

Discovering more than just engineering solutions to the problem, CrowdScience visits one of the world?s loudest cities, Mumbai in India. It is a place where noise has become a way of life. But is that all about to change?

Presenter: Alex Lathbridge Producer: Richard Walker Editor: Richard Collings

Welcome to Part 2 of our year-end extravaganza and the final episode of 2023!

We?ve had a brilliant year hunting down the answers to your science questions - on everything from food and phobias to friction and flying - and in this episode presenter Anand Jagatia is revisiting some of the best stories we covered. We?re bringing you some extra juicy bonus content that we couldn?t fit in to those shows first time round.

Hannah Fisher joins Anand to revisit an episode she produced about the microbiome, the community of tiny organisms living both on and inside us. During that show Hannah took presenter Caroline Steel to a microbiome museum in the Netherlands called Micropia. And one thing from Micropia that never got aired was the kiss-o-meter, a device that measures how many microbes you exchange when you kiss! Micropia curator Jasper Buikx explains the science behind the kiss-o-meter, and then Caroline Steel tries it for herself!

Microbes aren?t just living on and in humans and animals - they?re pretty much everywhere in our environment. And to illustrate this CrowdScience producer Marijke Peters brings Anand a bonus interview with a professional surfer who?s also a bioscientist.

Cliff Kapono undertook a scientific project travelling around the world to take microbiome samples from surfers in different countries. He discovered a fascinating global connection. Surfers are linked together by microbes on their skin that they get from the water around them. Intriguingly, he describes how this might affect our perception of who we are as humans.

Caroline Steel updates us on an interview she did with indigenous Australian astronomer Peter Swanton. Peter appeared on CrowdScience telling an ancient Australian folktale about a man who sacrificed himself to save his brother. The story, which has been handed down through several generations, provides possible evidence for an early observation of a supernova. You can hear that story in the episode ?Why is the sun at the centre??

Today we hear two extra stories that originally got cut from the broadcast due to time constraints. They are beautiful and poignant tales that reveal the depth of indigenous scientific achievement and the extraordinary significance of the night sky.

Presenter: Anand Jagatia Producer: Phil Sansom Editor: Richard Collings Production Co-ordinator: Jonathan Harris Studio Managers: Tim Heffer and Cath McGee

Featuring:

Jasper Buikx, scientific curator & spokesperson, ARTIS-Micropia Prof. Cliff Kapono, surfer & molecular bioscientist, School of Ocean Futures at Arizona State University Peter Swanton, indigenous research associate, Australian National University

Welcome to Part 1 of CrowdScience?s year-end extravaganza! It?s an extra-festive episode this week. For those who celebrate it, Christmas is the perfect time to pause and look back at the year just gone. Here on CrowdScience we?ve had a great 2023: we answered dozens of listener questions, ranging from climbing plants and ostriches to panic attacks and the weight of the internet.

This week presenter Anand Jagatia magically appears with a Santa?s sack full of special features. We?re catching up with some of our favourite guests from the past year and answering some of the extra questions that we never got the chance to cover.

First up we hear from presenter Tim Clare who we first heard in the episode ?Why do some people have panic attacks?? He takes Anand through his new book ? it's about board games: why we play them, how they?ve existed throughout history and what he?s learned about himself in the process of writing it.

Then it?s time for a bonus question. The CrowdScience team often get questions about noise pollution. One listener got in touch to ask whether the transition to electric vehicles will reduce this noise. Acoustic scientist Kurt Fristrup and epidemiologist Erica Walker give their perspectives on this question, and how sound and noise can sometimes be very different things. CrowdScience listener Marie - who originally starred in an episode about why she doesn?t have any sense of time - returns. Since the programme she has been speaking to psychologists about her problem and tells Anand what more she?s learnt.

We received another bonus question after a show in 2023 about AI: why can?t artificial intelligence be designed to explain it?s decisions? Producer Phil returns to data scientist Briana Brownell from the original episode to ask her why AI decision making is so very complex.

Finally, as it?s the season for holiday music, we?re asking what makes the genre so distinctive? Composer Jane Watkins - who originally created the sound of a panic attack for a CrowdScience episode - brings in her musical keyboard to demonstrate what makes a Christmas song so specifically ?a Christmas song?.

It?s all topped-off with the premiere of a happy and heart-warming song performed by the CrowdScience Christmas Choir ? a little gift for our loyal listeners.

Presenter: Anand Jagatia Producer: Phil Sansom Editor: Richard Collings Production Co-ordinator: Jonathan Harris Studio Managers: Tim Heffer and Cath McGhee

Featuring:

Tim Clare, author/poet/podcaster Dr. Kurt Fristrup, acoustic scientist, Colorado State University Prof. Erica Walker, RGSS Assistant Professor of Epidemiology, Brown University School of Public Health Marie Bergholtz Briana Brownell, data scientist Jane Watkins, composer

Seeds are crucial to human existence ? we eat them, we grow them and then we eat what they become. But what is a seed and how come it can sit there doing nothing for ages and then suddenly, when the conditions are right, burst into a plant?

That?s what CrowdScience listener Anke has been wondering. She runs an aquaponic salad farm near Stockholm in Sweden and she germinates thousands of seeds every week. With a bit of moisture and light, seeds that have been dormant for months can become leafy greens in just a few weeks. So are seeds alive, are they on some kind of life support, or is something else going on?

Presenter Caroline Steel sets off to Sweden to meet Anke, before heading for the Nordgen seed bank near Malmö. There she discovers how seeds being stored for future generations are tested for viability, and wonders what?s going on inside a seed that allows it to remain asleep before suddenly coming to life. How does a seed decide that the time is right?

We hear about one of the world?s longest running science experiments - a real-life treasure hunt that takes place every twenty years in Michigan, USA. Plant biologists tramp through the snow looking for bottles of seeds that were buried nearly a century and a half ago. Once found they try to germinate them. What superpowers does a seed need to be able to last that long?

Caroline also meets the woman who tried to grow date seeds that had been discarded at the palace of Herod the Great 2000 years ago, and ended up with previously extinct trees that produce delicious fruit. Surely a seed can?t have been alive for that long. Or can it?

Contributors:

Anke Johanna van Lenteren, Johannas Stadsodlingar, Sweden Johan Axelsson, Nordic Genetic Resource Center, Sweden Prof George Bassel, University of Warwick, UK Dr Grace Fleming, Michigan State University, USA Dr Sarah Sallon, Hadassah Medical Center, Israel

Presenter: Caroline Steel Producer: Ben Motley Editor: Richard Collings Production Coordinator: Jonathan Harris

(Photo: Hands holding spinach seeds. Credit: Vince Streano / Getty Images)

If, like this week?s Crowdscience listener Lili, you enjoy working out in the gym, you may have wondered where your fat disappears to when you exercise?

The short answer is that we convert it to energy that powers a whole range of physical processes - from breathing to walking as well as lying down and doing nothing. But the science behind energy expenditure is a little more complicated than that.

Presenter Anand Jagatia jumps on an exercise bike to have his metabolism measured and learns that he may be relying on an entirely different source of fuel as he works up a sweat.

Is all that hard work worth the effort it involves? Recent research suggests there is a limit to the number of calories humans can burn and that engaging in physical activity is not always a sure-fire way to keep trim.

So if working out is not the best way to lose weight, how about harnessing our own fat to tackle the complications of obesity? It used to be thought brown fat was exclusive to babies (and bears) but we now know adults have some of it too. Anand discovers that it appears to play a vital role in combatting a range of chronic diseases including hypertension and diabetes.

Presenter: Anand Jagatia Producer: Marijke Peters Editor: Richard Collings Production co-ordinator: Jonathan Harris

(Photo: Person squeezing their tummy. Credit: Getty Images)

*Warning* This episode includes references to suicide.

When listener Ben heard about a Kenyan ?starvation cult? in the news, he wondered whether the members of this group had been brainwashed. Is it possible to control someone?s mind?

In this episode presenter Caroline Steel learns how easily people can be influenced. She hears what it?s like to be part of a cult, and gets to the bottom of a decades-long debate: does brainwashing exist? And, if so, how does it work?

Presenter: Caroline Steel Producer: Florian Bohr Editor: Richard Collings Production Co-ordinator: Jonathan Harris Studio Managers: Donald McDonald and Emma Harth

Featuring:

Anthony Pratkanis, Emeritus Professor of Psychology, University of California, Santa Cruz Alexandra Stein, Honorary Research Fellow, University of Sussex Eileen Barker, Professor Emeritus of Sociology, London School of Economics

(Image: Washing a brain. Credit: Cemile Bingol / Getty Images).

CrowdScience listener Michael wants to know whether the brain responds differently if we listen to books instead of reading them. Do we retain information in the same way? And is there a difference between fiction and non-fiction?

Anand Jagatia finds out whether curling up with a good book is better than putting on his headphones. She is speaks to Prof Fatma Deniz from the Technical University of Berlin; Prof Naomi Baron from American University, Washington DC; Prof Patrick Nunn from the University of Sunshine Coast, Queensland and The Guesthouse Storytellers.

Presenter: Anand Jagatia Producer: Jo Glanville Editor: Richard Collings Production co-ordinator: Jonathan Harrison Sound engineer: Andrew Garratt

(Photo: Senior man wearing headphones listening to an audiobook. Credit: pixdeluxe/Getty Images)

Lying is something all humans do. We find it in every culture around the world. It?s in the world of work, in our relationships and online. It?s all pervasive and hard to escape.

Our question this week is from listener Anthony from Cambodia. He asked us to find out why we lie, and wants to know how conscious we are of the lies that we tell?

CrowdScience?s Caroline Steel is in the hot seat, on a journey where she will attempt to untangle the complex story behind lying.

It?s a subject scientists and psychologists have been studying for a long time. It?s also something writers, philosophers and theologists have been interpreting for thousands of years. But we?re only now really starting to get to grips with how it works as a human behaviour.

There are lies in our folklore, lies in the media and also lies in everyday conversation. It?s something we?ve all had to learn to navigate at some point in our lives. In this episode the CrowdScience team unravels the mysteries surrounding the behaviour and the art of lying.

Our journey will take us to meet the world?s ?second best liar?, an award she picked up at West Virginia?s Liar Contest. We?ll also meet a comedian who?s proud of the down-to-earth plain honesty of Dutch people.

An academic who has studied thousands of children?s brains will explain when we first start learning to lie. And we?ll hear about new research using magnetic resonance imaging, commonly known as MRI scans, which is helping to show how the more we actually lie, the less our brain reacts telling us not to.

Caroline looks at how lying changes from culture to culture. Do we really all lie? And do we lie in the same way?

The surprising and intriguing answer is found in how early it develops in us as a human behaviour.

Contributors:

Prof Kang Lee, Professor in Applied Psychology and Human Development at Ontario Institute for Studies in Education, University of Toronto Prof Tali Sharot, Professor of Cognitive Neuroscience at University College London Ian Leslie, journalist and author of ?Born Liars? Ariana Kincaid, Champion Liar at West Virginia Liars Contest Derek Scott Mitchell, actor and comedian | @letsdoubledutch on Instagram Readings by Kitty O'Sullivan

Presenter: Caroline Steel Producer: Robbie Wojciechowski Editor: Richard Collings Production Co-ordinator: Jonathan Harris Studio Managers: Emma Harth, Donald MacDonald, Andrew Garratt

(Photo: Young Businessman Interviews for new job. Credit: Andrew Rich/ Getty Images)

Our planet is quickly approaching 1.5 degrees Celsius of warming (2.7 degrees Fahrenheit). Scientists say we might cross this milestone in just six years. Listener Julian wants to know what life will look like on the other side of that threshold.

With the help of climate scientists, the BBC?s Anand Jagatia dives into the worlds of virtual climate models. From heatwaves to higher humidity indices to extreme precipitation and drought, he gets a picture of what's to come.

We also venture to places that are warming both faster and more slowly than the global average.

In a remote village in Alaska residents are already dealing with life-changing permafrost thaw and ground that's melting beneath their feet. Permafrost expert Sue Natali tells us what this unexpected thawing ground means for the planet as it releases carbon and methane we weren't necessarily counting on.

In Indian cities, temperatures were already high, but they're not rising as quickly as climate scientists had initially predicted. We hear why this is and why it might be a big problem in the not- too-distant future.

Anand also speaks to television series writer Dorothy Fortenberry about how science informed plotlines in her new show Extrapolations.

This episode is not just about what climate change will bring -- but what it will feel like.

Presenter: Anand Jagatia Producer: Sam Baker Reporters: Sunni Bean & Chhavi Sachdev Editor: Richard Collings Production Co-ordinator: Jonathan Harris Studio Manager: Tim Heffer

Featuring:

Dorothy Fortenberry, Extrapolations, Apple TV Tom Matthews, Department of Geography, King's College London Sue Natali, Woodwell Climate Research Center Morris Alexie, Tribal Liaison, Alaska Native village of Nunapicuaq (Nunapitchuk) Rakesh Kumar, India?s Council of Scientific and Industrial Research (Photo: Two children look out at floating sea ice. Credit: StutterStockX / Getty Images)

?You are what you eat? is a well-known saying. But is it really true? That?s what we explore in this week?s CrowdScience thanks to a question from listener Claire from Australia.

We each have trillions of tiny microbes and bacteria inside our bodies, living in our mouths, skin, ears and even in our eyes. Each community of microbes and bacteria is known as a microbiome. The most populous of these is in our gut, with hundreds of trillions of organisms and bacteria helping digest the food we eat.

Our gut microbiome is affected by lots of things but mainly by our diet. With our gut microbiome forming such a massive part of our insides, people have long suspected that what we eat impacts how we feel.

Presenter Caroline Steel investigates. She speaks to a professor of Psychiatry, Jane Foster, to find out how interconnected our microbiome and our brain really are. Professor Foster also explains the different ways in which our microbiome and brain communicate.

Do we really know what role diet plays in mental health? Consultant psychiatrist Professor David Veale provides more detail. And at a café with a rather interesting menu, Caroline samples some of the food available as occupational therapist Joel Oliver explains how important food can be as part of mental health treatment.

This begs the question: if our microbiome really does influence our mental health, can we harness the power of microbes to potentially find new treatments to help our mental health? Dr Najaf Amin tells us about her research identifying the link between specific microbes and depression.

Producer: Hannah Fisher Presenter: Caroline Steel Editor: Richard Collings Production Coordinator: Jonathan Harris Studio Manager: Bob Nettles

(Photo: Young hipster man eating salad. Credit: Tara Moore / Getty Images)

Why are some animals cute, cuddly, adorable ? and some are slimy, creepy and downright weird? This edition of Crowdscience, recorded in front of a live audience, comes to you directly from the world-famous Green Man Festival in Bannau Brycheiniog National Park in Cymru (Wales). The programme recording was powered entirely by hydrogen.

Our inbox has been bursting at the seams with questions about creepy crawlies, deep sea beasties, cheeky monkeys, endangered species and animals of all shapes and sizes. So, we rounded up a panel of experts to get some answers!

Surrounded by 25,000 people trudging merrily through the mud, pelted with torrential rain, underscored by the warm hum of revelry, the BBC?s Marnie Chesterton speaks with Dr David Jones from the Natural History Museum, an expert on creepy crawlies and someone who spends a considerable amount of time thinking about earthworms, ants, and termites. Also joining us is Jess Savage, a researcher from the Institute of Zoology in London who?s an expert on ocean-dwelling animals and the impact of plastic pollution. Finally, we have Simon Watt, a biologist, comedian and founder of the Ugly Animal Preservation Society.

Join us for this very special edition of Crowdscience, in partnership with Green Man Festival, where we bring the experts closer to you than ever before.

Presenter: Marnie Chesterton Producer: Emily Bird Editor: Richard Collings Technical producer: Mike Cox Studio manager: Jackie Margerum Production co-ordinator: Jonathan Harris

(Photo: Marnie and guests. Credit: Jonathan Harris)

Salmon are one of the world?s most popular fish. And - in terms of the size of the industry - they?re also the world?s most valuable. They provide crucial proteins and fatty acids to many people?s diets. But like other species of fish, their production is undergoing a historic change. Plenty of salmon is still caught from the wild, but the majority is now farmed off the coasts of countries like Norway or Chile. With global demand on the rise, listener Jodie from Australia wants to know: which is healthier, farmed salmon or wild?

CrowdScience?s Marnie Chesterton is on the case! Her first stop: a remote loch in the west of Scotland, where salmon company Mowi rears thousands of the fish in big, open-water nets. Marnie takes the chance to see for herself what salmon farming actually looks like. She then speaks to aquaculture nutritionist Stefanie Colombo, who researches the nutrient content of different types of salmon. Stefanie breaks down the health positives and negatives of each, as well as what causes some of these differences.

Crucially, farmed salmon will vary in nutrition depending on where you are in the world. Jodie, the listener who asked this week?s question, is from Australia so her fish will most likely come from Tasmania. Chemist Christian Narkowicz has been conducting chemical tests on the salmon there - he tells Marnie what he?s found.

When we ask which type of salmon is healthier, it?s also important to consider the issue of environmental health. Eilís Lawlor is an economist and the author of a report on externalities and unintended consequences of the global salmon industry. She and Marnie discuss problems of overfishing and environmental pollution.

It?s also necessary to understand where wild salmon comes from. Marissa Wilson, director of the Alaska Marine Conservation Council, explains her average day out at sea and talks about some of the consequences of industrial offshore fishing.

Finally, we ask if there?s a way to improve farmed salmon by moving it onto land? That?s Yonathan Zohar?s mission. In the basement of the Institute for Marine and Environmental Technology in Baltimore, USA, he keeps several tanks of salmon in artificial seawater, using bacteria to dispose of the waste. Is this where salmon farming is headed? Or is the future more complex?

Presenter: Marnie Chesterton Producer: Phil Sansom Production Co-ordinator: Jonathan Harris Editor: Richard Collings

(Photo: Atlantic Salmon jumping out of the water. Credit: Kevin Wells / Getty Images)

CrowdScience listener Kristine from Wisconsin in the USA wants to know why herbs and spices taste so good to so many of us. She?s intrigued to know if there's evidence that herbs and spices can keep us healthy.

Anand Jagatia visits the historic naval city of Portsmouth in the UK, where exotic spices from around the world were first brought in from the East Asia more than 600 years ago.

He?s on a journey to find out why many of us think spices are delicious. But are there also nutritional benefits to seasoning our food with them? Anand asks what science or studies are there to show that eating herbs and spices can be beneficial for our health?

Presenter: Anand Jagatia Producer: Joanna Hall Assistant Producer: Jonathan Harris Editor: Richard Collings Studio Technicians: Bob Nettles & Steve Greenwood

Contributors:

Prof. Lindell Bromham, evolutionary biologist, Australian National University Dr. Kanchan Koya, Molecular Biologist and founder of the Spice Spice Baby website Dr. Beronda L. Montgomery, plant biologist and Dean at Grinnell College, Iowa, USA Dr. Lorenzo Stafford an olfactory researcher, Department of Psychology, University of Portsmouth, UK

(Photo: A couple stand at a spice shop. Credit: Thomas Barwick / Getty Images)

Humans have an outsized impact on the planet: we?ve wreaked havoc on countless ecosystems and one study estimates only 3% of land on Earth remains untouched by our influence. CrowdScience listener Teri has witnessed the harmful effects of development on natural habitats near her home, and wonders whether we can ever function as part of a healthy ecosystem.

We look for answers in Teri?s home state, California. Humans have lived here for over 10,000 years and its first inhabitants formed a connection to their landscape unlike the exploitative approach of many later settlers. Today, the beliefs and traditions of the Karuk Tribe of northern California still emphasise a symbiotic relationship with nature, seeing plants and animals as their relations.

Over the past couple of centuries much of the Karuk?s land has been degraded by mining, the timber industry and the outlawing of traditional burning practices. Tribal members show us how they?re working to try to restore ecological balance.

As for the rest of humanity: can we rein in our destructive relationship to nature; or even have a beneficial effect on our local ecosystems?

Contributors:

Kathy McCovey - Karuk Tribe member and cultural practitioner Dr Steward Pickett - Ecologist, Cary Institute of Ecosystem Studies Bill Tripp - Karuk Tribe member and Director of Natural Resources and Environmental Policy, Karuk Tribe Department of Natural Resources Dr Frank Kanawha Lake - US Forest Service Research Ecologist and Tribal Liaison Will Harling - Co-lead, Western Klamath Restoration Partnership

Presenter: Caroline Steel Producer: Cathy Edwards Editor: Richard Collings Production Co-ordinator: Jonathan Harris Studio Manager: Giles Aspen & Steve Greenwood

(Image: Huckleberries and tanoak acorns gathered near a burn site. Credit: Stormy Staats)

It's pretty obvious to each of us that we are conscious, as we go about our days and feel the experience of just ?being ourselves'. But how do we know that someone else is conscious?

It?s something we lose during dreamless sleep, under anaesthesia or in a coma. But what exactly is consciousness? On the one hand, it?s pretty obvious - it?s what we all feel as we go about our daily lives. It's the experience of 'being you'. On the other hand, it gets pretty tricky when we try to pin down the science of it all. How do we know that someone (or something) else is conscious?

CrowdScience listener Sylvester was wondering about this and he got in touch with a few questions on the subject. What is the relationship between our consciousness and reality? Is it all just a hallucination? When does it start and stop? Does consciousness reside in a particular part of the brain?

Host Marnie Chesterton sets out to tackle this elusive but utterly fundamental quality of life and sees how researchers are attempting to conceptualise and study it.

In the relatively young field of consciousness multiple theories have emerged. A new way of testing them - an adversarial collaboration - is offering a novel approach to not just consciousness research but science more broadly. We visit one lab in Frankfurt that's running experiments for the most recent adversarial collaboration and trying to test two theories of consciousness ? Global Neuronal Workspace Theory (GNW) and Integrated Information Theory (IIT) ? against each other.

Looking at these and other concepts of consciousness like Qualia, Marnie tries to understand this central tenet of our human experience that, in many ways, remains one of the great mysteries of science.

Presenter: Marnie Chesterton Producer: Sam Baker Editor: Richard Collings Production Coordinator: Jonathan Harris Studio Manager: Sarah Hockley Featuring:

Anil Seth, Sussex Centre for Consciousness Science, University of Sussex in Brighton, England Lucia Melloni, Max Planck for Empirical Aesthetics in Frankfurt, New York University & Project Lead for COGITATE Nao Tsuchiya, Monash Data Futures Institute, Turner Institute for Brain & Mental Health, Monash University

(Image: Active Human Brain. Credit: PM Images / Getty Images)

Philosophers have long pondered the concept of a brain in a jar, hooked up to a simulated world. Though this has largely remained a thought experiment, CrowdScience listener JP wants to know if it might become reality in the not-too-distant future, with advances in stem cell research.

In the two decades since stem cell research began, scientists have learned how to use these cells to create the myriad of cell types in our bodies, including those in our brains, offering researchers ways to study neurological injuries and neurodegenerative disorders. Some labs have actually started 3D printing stem cells into sections of brain tissue in order to study specific interactions in the brain. Human brain organoids offer another way to study brain development and diseases from autism to the Zika virus.

So, might stem cell research one day lead to a fully-grown human brain, or is that resolutely in the realm of science fiction? If something resembling our brains is on the horizon, is there any chance that it could actually become conscious? And how would we even know if it was?

Host Marnie Chesterton takes a peek inside the human brain and speaks with leading scientists in the field, including a philosopher and ethicist who talks about the benefits ? and potential pitfalls ? of growing human brain models. Along the way, we'll pull apart the science from what still remains (at least for now) fiction.

Presenter: Marnie Chesterton Producer: Sam Baker Assistant Producer: Jonathan Blackwell Editor: Richard Collings Production Coordinator: Jonathan Harris Studio Manager: Jackie Margerum

(Image: Brain in a jar. Credit: Mike Kemp / Getty Images)

Everyone has fears ? but what makes a fear become a phobia? Why are some people scared of spiders (arachnophobia), buttons (koumpounophobia), or the colour yellow (xanthophobia)? Or why are others are scared of situations, like small spaces (claustrophobia), empty rooms (kenophobia) or heights (acrophobia)?

This is a question which has been bothering Crowdscience listener Scott, who has a phobia of bridges. He gets anxious and panicky when driving over bridges and is scared he?ll lose control of the car. It?s also a question that struck a chord with presenter Caroline Steel. She is claustrophobic, particularly in lifts, steering clear of them at all costs and even once climbing nine flights of stairs in crutches to avoid using the lift.

But where do these phobias come from and why do some people have them and not others? To investigate, Caroline speaks to experts to discover where phobias come from, why we have them and how they develop. And she visits a psychologist to learn about different types of treatment for phobias, and to receive treatment herself in the hope that one day, maybe she?ll be able to take the lift instead of the stairs.

Contributors:

Professor Paul Salkovskis, Director, Oxford Centre for Psychological Health, UK Professor Ekaterina Likhtik, Associate Professor in Biological Sciences at Hunter College, CUNY, USA Dr Andras Zsido, Senior Research Fellow at the Institute of Psychology, University of Pécs, Hungary

Presenter: Caroline Steel Producer: Hannah Fisher Editor: Richard Collings Production Co-ordinator: Jonathan Harris

(Image: Person sitting on high up bridge. Credit: ljubaphoto / Getty Images)

CrowdScience listener Leo gets stressed when his young children start screaming at the same time in the middle of the night. He wants to know why we haven?t evolved to deal with the stress more effectively. The challenges of bringing up a family are nothing new and we don?t face the same dangers as our ancestors, so why do we still react as if it?s a life-threatening emergency? Caroline Steel finds out what stress is for, what it does to us and whether we have in fact evolved to manage it.

Contributors:

Tashfia Ahmed, biomedical engineer, post-doctoral researcher, City University, London Anne-Kathrin Gellner, neurologist and psychiatrist, Bonn University James Rilling, anthropologist and neuroscientist, Department of Psychology and Department of Psychiatry and Behavioural Sciences, Emory University Gunter Wagner, evolutionary biologist, Vienna University

Presenter: Caroline Steel Producer: Jo Glanville Editor: Richard Collings Production Co-ordinator: Jonathan Harris Studio Manager: Jackie Margerum

(Image: Frustrated father holds baby in his arms. Credit: Jamie Grill / Getty Images)

Many of us are worried about the environment, but the aim of living in a truly sustainable way is hard to pin down. Do we all need to stop buying things? Is it down to governments to make the changes for us? Is there somewhere in the world painting a picture of the end goal?

It?s a question that has bothered CrowdScience listener Cate for 20 years! She?s worried we?re not doing enough for the environment and just wants a clear scenario of what it might look like to live sustainably, in a way that could work for all eight billion of us on the planet.

It?s a big question, so this week presenter Caroline Steel has teamed up with her friend and colleague Graihagh Jackson from The Climate Question podcast to answer it.

They head to the remote Danish island of Bornholm in the Baltic Sea, which is aiming to go carbon neutral by 2025 and zero waste by 2032. How are they going about it and could this be replicated elsewhere? We visit a ground-breaking project turning nappies into compost, meet a glassblower making tableware out of wasted insulin vials, and find out how pig waste can power homes.

This edition of CrowdScience hones in on Bornholm?s zero waste goal. Will the island make it?

Listen to The Climate Question?s look at the island?s quest to go carbon neutral here: BBC World Service - The Climate Question, Going carbon neutral - lessons from Denmark - www.bbc.co.uk/programmes/w3ct5bkg (Available from 3rd September)

Presenters: Caroline Steel and Graihagh Jackson Producer: Sophie Eastaugh Editor: Richard Collings Production Coordinator: Jonathan Harris

(Image: Dr David Christensen, Project Manager at BOFA, Bornholm?s waste authority with presenter Caroline Steel in front of a giant mound of waste bound for the island?s incinerator. The incinerator will be shut down in 2032 when the island aims to be zero waste. Credit: Sophie Eastaugh)

For hundreds of millions of years insects controlled the skies. Before birds, bats and pterodactyls, insects were the only creatures that had evolved the ability to fly: a miracle of physics and physiology requiring their bodies to act in coordinated ballet.

This week three separate CrowdScience listeners have been asking questions about the flight of butterflies and moths. How do they move so erratically, yet land so precisely? What makes such tiny insects such accurate flyers?

Presenter Anand Jagatia -- not the biggest fan of either butterflies or moths -- visits Butterfly Paradise at London Zoo to meet keeper Mark Tansley. Anand tries to get over his aversion by immersing himself in fluttering creatures.

He then meets insect flight expert Sanjay Sane to learn the hidden mechanics behind their aeronautical skills: the vortexes of air generated by their wings and the complex muscle architecture inside their torsos. Next, aerospace engineer Amy Lang explains how the scales on their wings reduce air resistance by clever manipulation of the air and how this function trades off against other uses of the scales: for colour, for keeping dry, and much more.

All of these abilities are put to the test during the incredible global migrations that some butterflies undertake. Gerard Talavera tells Anand how he turned previous thinking about butterfly migration across Africa on its head.

Presenter: Anand Jagatia Producer: Phil Sansom Voiceover: Kitty O?Sullivan Production Coordinator: Jonathan Harris Editor: Richard Collings

(Photo: Crowdscience presenter Anand Jagatia crouches next to a butterfly. Credit: Phil Sansom)

How do you think about the internet? What does the word conjuror up? Maybe a cloud? Or the flashing router in the corner of your front room? Or this magic power that connects over 5 billion people on all the continents of this planet? Most of us don?t think of it at all, beyond whether we can connect our phones to it.

CrowdScience listener Simon has been thinking and wants to know how much it weighs. Which means trying to work out what counts as the internet. If it is purely the electrons that form those tikitok videos and cat memes, then you might be surprised to hear that you could lift of the internet with 1 finger. But presenters Caroline Steel and Marnie Chesterton argue that there might be more, which sends them on a journey.

They meet Andrew Blum, the author of the book Tubes ? Behind the Scenes at the Internet, about his journey to trace the physical internet. And enlist vital help from cable-loving analyst Lane Burdette at Telegeography, who maps the internet.

To find those cables under the oceans, they travel to Porthcurno, once an uninhabited valley in rural Cornwall, now home to the Museum of Global Communications thanks to its status as a hub in the modern map of worldwide communications. With the museum?s Susan Heritage-Tilley, they compare original telegraph cables and modern fibre optics.

The team also head to a remote Canadian post office, so correspondent Meral Jamal can intercept folk picking up their satellite internet receivers, and ask to weigh them. A seemingly innocuous question becomes the quest for everything that connects us, and its weight!

Producer: Marnie Chesterton Presenter: Marnie Chesterton & Caroline Steel Editor: Richard Collings Production Coordinator: Jonathan Harris

(Image: Scales with data worlds and symbols interspersed throughout. Credit: Getty Images)

Dogs have been our best animal buddy for thousands of years. They?ve helped us out in countless ways from hunting alongside us to guiding us as service dogs. Talk to any pet owner and they?ll tell you how much joy their dog brings them. But you?ll also probably hear about vets bills, muddy footprints, or chewed up slippers. There are plenty of claims about the ways in which dogs might benefit our physical and mental health -- but how strong is the evidence?

This week on CrowdScience, listeners Jason and Finn in Guernsey want to know if there?s any real evidence that our furry friends can benefit our health and wellbeing.

Join Anand Jagatia as he enlists the help of his own pup, Stella, to explore the evidence. He uncovers the profound effects that service dogs can have on the mental health of military veterans in the US. Anand ponders the strangely unique relationship between humans and dogs and we learn about the surprising ways that about growing up with a pet dog can impact your health.

Presenter: Anand Jagatia Producer: Emily Bird Editor: Richard Collings Studio Engineer: Donald MacDonald Production coordinator: Jonathan Harris, Elliott Prince

Contributors: Dr Kerri Rodriguez Professor Tove Fall Professor Hal Herzog

(Photo: Jack Russell leaping into the air trying to catch a ball. Credit: Brighton Dog Photography/Getty Images)

Imagine spending six months of every year living in total shade. That?s what life is like for residents of the Norwegian town of Rjukan, set so low in a valley that they see no direct sunshine at all from October to March.

Marnie Chesterton heads there to hear about an ingenious solution: giant mirrors that beam rays down into the town square, where locals gather to feel the reflected heat.

The man behind the project was motivated by a need for winter sun ? but how much difference does it really make to our health and happiness? That?s the question posed by this week?s CrowdScience listener Michael, who has noticed living in the rainy Australian city of Melbourne is taking its toll.

Many pensioners claim sunshine relieves achiness as well as conditions like arthritis but one of the biggest scientific studies found temperature has no real impact on reported pain levels, while factors like air pressure and humidity may play a role.

When it comes to our mood, it seems that spending time outside is more important than feeling the heat. The optimum temperature for wellbeing is around a cool 19 degrees centigrade, while excessive warm weather has been linked to an increase in violence and crime.

You can watch a visualisation of this episode on YouTube: Is the 'sunshine cure' a real thing? - CrowdScience, BBC World Service podcast - YouTube

Producer: Marijke Peters Presenter: Marnie Chesterton Editor: Richard Collings Production co-ordinator: Jonathan Harris

Contributors:

Dr Anna Beukenhorst, University of Manchester Professor Oscar Ybarra, University of Illinois Professor Solomon Hsiang, University of California, Berkeley Martin Andersen, artist

(Photo: Young woman enjoying sunset. Credit: Muriel De Seze/Getty Images)

Imagine spending six months of every year living in total shade. That?s what life is like for residents of the Norwegian town of Rjukan, set so low in a valley that they see no direct sunshine at all from October to March. Marnie Chesterton heads there to hear about an ingenious solution: giant mirrors that beam rays down into the town square, where locals gather to feel the reflected heat. The man behind the project was motivated by a need for winter sun ? but how much difference does it really make to our health and happiness? That?s the question posed by this week?s CrowdScience listener Michael, who has noticed living in the rainy Australian city of Melbourne is taking its toll. Many pensioners claim sunshine relieves achiness as well as conditions like arthritis but one of the biggest scientific studies found temperature actually has no impact on reported pain levels, while factors like air pressure and humidity may play a role. When it comes to our mood, it seems that spending time outside is more important than feeling the heat and the optimum temperature for wellbeing is around a cool 19 degrees centigrade, while excessive warm weather has been linked to an increase in violence and crime.

Contributors: Dr Anna Beukenhorst, University of Manchester Professor Oscar Ybarra, University of Illinois Professor Solomon Hsiang, University of California, Berkeley Martin Andersen, artist

(Image: Man with smoke coming out of ears. Credit: Getty Images)

CrowdScience investigates the link between music and emotion to try and understand why certain songs can have such a profound impact on our mood.

From breakup songs to upbeat holiday hits, many of us have made playlists that reflect how we feel, whether that?s down in the dumps or high as a kite. This week CrowdScience investigates the link between music and emotion to try and understand why certain songs can have such a profound impact on our mood.

Presenter Anand Jagatia is surprised to learn that newborn babies are more likely to fall asleep when listening to fast tempo happy tunes than soothing sad lullabies, which may be because they?re attuned to multiple auditory stimuli after months in the womb.

But later in life we actually seek out sad songs to make us feel better. The so-called ?sadness paradox? has been studied for many centuries. But what is it about melancholy music that might be good for us?

Some scientists believe more empathetic people enjoy listening to these types of tune because they elicit a feeling of compassion towards others, which can be rewarding.

A film composer tells us how scoring suspense isn?t simply about minor or major chords, or even what instruments you use ? it all comes down to keeping the audience guessing about what?s coming next.

(Photo: young woman listening to headphones looking sad. Credit: Getty Images)

Presenter: Anand Jagatia Producer: Marijke Peters Production co-ordinator: Jonathan Harris Editor: Richard Collings Studio Technician: Phil Lander

Contributors:

Alex Heffes Professor Stefan Koelsch Dr Emese Nagy Associate Professor Jonna Vuoskoski Dr Scott Bannister

?I?m bored!? We can all relate to the uncomfortable - and at times unbearable - feeling of boredom. But what is it? Why does it happen? And could this frustrating, thumb-twiddling experience actually serve some evolutionary purpose?

CrowdScience listener Brian started wondering this over a particularly uninspiring bowl of washing up and it?s ended with presenter Marnie Chesterton going on a blessedly un-boring tour through the science and psychology of tedium.

She finds out why some people are more affected than others, why boredom is the key to discovery and innovation and how we can all start improving our lives by embracing those mind-numbing moments.

(Photo: Bored kids on a park bench. Credit: Getty Images)

Presenter: Marnie Chesterton Producer: Samara Linton Production co-ordinator: Jonathan Harris Editor: Richard Collings

Contributors: Professor James Danckert, University of Waterloo, Canada Dr Elizabeth Weybright, Washington State University Dr Christian Chan, Hong Kong University Annie Runkel, University of Dundee

Why are some people left-handed? Why are some people right-footed? Why do some write with their right and throw a ball with their left? What does this all have to do with our brains? Why is it hard for some people to tell left from right? And what about animals? Can they be left-flippered, or finned, or southpawed? That's what a few CrowdScience listeners want to know, and we've got an expert panel on left, right and everything in between to help answer your questions.

From genetics to culture, host Caroline Steel works to unpack what's known and what's still unknown about handedness.

David Carey from Bangor University helps Caroline better understand her own mixed-handedness through a series of simple tests and shares some insights into what role handedness (and footedness) plays in the world of sports. Neuropsychologist Marietta Papadatou-Pastou from National and Kapodistrian University of Athens helps break down the numbers on left v. right-handedness and its cultural influences. To better understand the genetics and evolution of handedness, we hear from Sebastian Ocklenburg from Medical School Hamburg, who has investigated the phenomenon in other species.

Throughout the show, Caroline tries to understand why handedness exists in the first place and why our species is so biased to the right. She tries to answer listener Barb?s question as to why ambidexterity isn?t more ubiquitous, and it leads to some brainy tangents. We also hear questions from listeners Scotia and Roland, and travel to India with BBC reporter Chhavi Sachdev to hear how cultural norms are not in favour of lefties.

Presenter: Caroline Steel Producer: Sam Baker Editor: Richard Collings Production co-ordinator: Jonathan Harris Studio engineers: Tim Heffer, Steve Greenwood

Featuring:

Marietta Papadatou-Pastou, Neuropsychologist and Assistant Professor, National and Kapodistrian University of Athens Sebastian Ocklenburg, Professor for Research Methods, Medical School Hamburg David Carey, Reader in Neuropsychology, Bangor University

(Image: Close up of group of hands raised. Credit: JGI/Getty Images)

CrowdScience listener Ali wants to know why we experience vertigo.

Anand Jagatia finds out that it?s not just the giddy sensation we feel when we?re at the top of a mountain. Vertigo is also a physical illness that can be triggered by a range of disorders.

He talks to leading experts on balance to learn what causes the condition, discovers how virtual reality can help people with a phobia of being in high places and volunteers to be turned upside down to experience what it feels like to be treated for vertigo.

Contributors:

Peter Rea, consultant ENT surgeon, University Hospitals of Leicester, Honorary Professor of Balance Medicine, De Montfort University, Honorary Professor in Life Sciences, University of Leicester, UK Tammy Barker, clinical scientist, Balance Centre, Leicester Royal Infirmary, UK Rupal Rajani, broadcast journalist and member of Life on the Level Tara Donker, clinical psychologist, Freiburg University, Germany Andrew Hugill, composer, musicologist and deputy director, Institute for Digital Culture, University of Leicester, UK

Presenter: Anand Jagatia Producer: Jo Glanville Editor: Richard Collings Production co-ordinator: Jonathan Harris Sound design: Julian Wharton Studio manager: Bob Nettles

With thanks to Andrew Hugill for permission to include his composition Verdigrade, commissioned by The Space as part of ?Culture in Quarantine?, BBC.

Image: CrowdScience presenter Anand Jagatia tries out a machine for diagnosing and treating vertigo at Leicester Royal Infirmary Credit: Peter Rea

We all enjoy a deep-fried Mars bar with french fries from time to time, but why do we crave these unhealthy foods instead of healthy things like spinach or broccoli? And what is a food craving? The answers lie in a complex blend of our psychology, physiology, and even sociology.

BBC CrowdScience presenter Alex Lathbridge savours a mystery-meat crocket with the experts on a quest to discover the hidden sources and sauces of our food cravings.

Presenter: Alex Lathbridge Producer: Richard Walker Editor: Richard Collings

(Image: Stack of cheeseburgers and French fries. Credit: Dominic Lipinski/PA)

Please note: This is a shorter version than the original podcast. A longer version is available here - https://www.bbc.co.uk/sounds/play/w3ct3j6y.

Humans can walk for miles, solve problems and form complex relationships using the energy provided by daily meals. That is a lot of output for a fairly modest input. Listener Charlotte from the UK wants to know: how efficient are humans? How do they compare to cars, other animals and even to each other?

Presenter Marnie Chesterton pits her energetic self against everything from cars to rabbits to find out how she shapes up.

Marnie also explores whether humans are born equal when it comes to fuel efficiency. Does the energy from one banana get converted into the same amount of movement from person to person? Marnie gets on a treadmill to find out how efficient she really is. With contributors from Herman Pontzer, Duke University, Rhona Pearce, Loughborough University and Christian Gammelgaard Olesen from Wolturnus wheelchair manufacturing company.

Presenter: Marnie Chesterton Producer: Caroline Steel Editor: Richard Collings Production co-ordinator: Jonathan Harris

(Image: Illustration of an airplane, a red car and a female wheel chair user. Credits: Getty Images)

CrowdScience listener Eileen cannot see images in her head of her memories. She only discovered by chance that most other people can do this. She wants to know why she can?t see them and if it is something she can learn to do.

Anand Jagatia finds out what mental images are for and whether scientists know why some people can?t create them.

Three per cent of the world?s population cannot see mental images like Eileen. And it is only recently been given a name ? aphantasia.

Anand discovers why mental images are useful, why they are sometimes traumatic and how people who are blind or visually impaired can also create images of the world around them.

Contributors:

Emily Holmes, professor of clinical psychology, Uppsala University, Sweden Adam Zeman, professor of cognitive and behavioural psychology, Exeter University, UK Joel Pearson, professor of cognitive neuroscience, University of New South Wales, Australia Paul Gabias, associate professor, Department of Psychology, University of British Columbia, Canada Marijke Peters, Hannah Fisher and Jo Glanville, CrowdScience producers

Presenter: Anand Jagatia Producer: Jo Glanville Editor: Richard Collings Production co-ordinator: Jonathan Harris Sound: Jackie Margerum

Image credit: Andriy Onufriyenko | GETTY IMAGES | Creative #1397973635

Welcome to the exciting new field of generative artificial intelligence - or generative AI. We?re not talking about robots or spaceships: instead these are image generators and chatbots that are already revolutionising the way people write, research and interact in the virtual world. Their capabilities are extraordinary. But before they can produce results they first need to be trained on vast amounts of data. And that?s what got CrowdScience listener Ian wondering. He says: ?Before long, much of the material on the internet will have been written, or at least co-written, by AIs. What will happen when AIs are being trained on texts they have written themselves??

To answer this question Anand Jagatia first meets artist and scientist Michelle Huang. Michelle recently embarked on a therapy project to try and connect with her own ?inner child?. She took a decade?s worth of her diaries from her childhood and fed them into an AI to try and simulate a conversation between her and her younger self. Can a machine convincingly recreate the voice of a human being? You can be the judge!

Then, data scientist Briana Brownell joins Anand to explain a little about how ?generative AI? like this actually works. Together they open up the popular chatbot, ChatGPT, to put it to the test: but can it help Anand solve his personal conundrum? Now that we understand what AI is capable of we also need to know its limits. AI researcher Pablo Villalobos describes the process of training generative AI and where it gets its material from. The amount of data consumed in this way keeps going up and up, Pablo and his colleagues have been calculating exactly when that data is likely to run out. Pablo also discusses recent research exploring a unique effect that occurs if AI is repeatedly trained on its own material. Finally, Briana Brownell returns to cover a range of wider issues related to artificial intelligence and what effects it might have on our future.

Presenter: Anand Jagatia Producer: Phil Sansom Editor: Richard Collings

CrowdScience listener Nyankami, from Kenya, has a friend with dementia. Despite memory loss and no longer knowing his way around, his friend has no problem communicating. So what?s the connection between memory and language?

Caroline Steel discovers how dementia affects our speech. In most cases the illness does have an impact on our ability to speak but it can depend on many factors, including the type of dementia and even how many languages we speak.

She meets George Rook, diagnosed with vascular dementia and Alzheimer?s, who?s a passionate campaigner for people with dementia and talks to dementia nurse Helen Green, who explains how the illness can affect our behaviour.

She discovers that speaking more than one language can actually protect our brains from decline and finds out about cutting edge research that is helping people with dementia to improve their memory and capacity to speak.

Featuring: George Rook, Lived Experience Advisory Panel, Dementia UK Helen Green, Admiral Nurse, specialising in dementia Professor Alex Leff, Professor of Cognitive Neurology, Institute of Neurology, University College London Professor Guillaume Thierry, Professor of Cognitive Neuroscience, Bangor University Professor Yan Jing Wu, Professor of Neurolinguistics, Ningbo University, China Dr Elizabeth Kuhn, Post-Doctoral Fellow, German Centre for Neurodegenerative Disease, Bonn

Image Credit: Emma Innocenti

Presenter: Caroline Steel Producer: Jo Glanville Editor: Richard Collings Production co-ordinator: Jonathan Harris Sound engineer: Jackie Margerum

It may seem like a simple question but could you explain why the earth revolves around the sun? That is what listener Josh from New York wants to know. For much of human history we thought everything revolved around us, literally. So how did humans come to the conclusion that we're not the centre of the universe? And how did the scientific process help us uncover the true order of things?

Looking through telescopes from the vantage point of Australia, host Caroline Steel speaks with astronomers and physicists about the bumpy scientific journey to arrive at this discovery that we now take for granted. Delving into Indigenous astronomy with researcher Peter Swanton, Caroline questions whether Western scientists were really the first ones to grasp this understanding of our solar system.

And at the Sydney Observatory, stellar astrophysicist Devika Kamath and Sydney Observatory host Nada Salama show Caroline some of the clues up in the sky that astronomers in the 1600s used to deduce that there was something wrong with earlier models of our solar system.

Rhett Allain from Southeastern Louisiana University helps break down the physics concepts at play when it comes to the motion of our planets and the sun.

Through her exploration of a seemingly simple question, Caroline asks some big questions as she looks up to the stars ? about life, the universe, and the nature of science itself.

Producer: Sam Baker Presenter: Caroline Steel Editor: Richard Collings Production co-ordinator: Jonathan Harris

Featuring: Devika Kamath, Astrophysicist, Macquarie University Rhett Allain, Associate Professor, Southeastern Louisiana University Peter Swanton, Indigenous Research Associate, Australian National University

(Photo: Caroline and Devika, Sydney Observatory)

Anyone who has ever enjoyed a beach holiday will know there?s something special about being by the seaside. But does sea swimming actually have tangible health effects? This week?s listener Holly is a self-confessed water baby, and says her regular surf sessions on Sydney?s iconic Bondi beach make her feel happier and look younger. But could we get some of the benefits from the beach without getting our feet wet?

At the Plymouth Marine Lab, researchers have shown that the smell of the sea makes most people feel happier. They?re measuring sea spray aerosols containing natural compounds derived from algae, that dial down the inflammatory response in lung cancer cells. Other scientists in the region have investigated the use of virtual reality to simulate being by the coast, which is proven to reduce the experience of dental pain during treatment. Finally, we visit Teats Hill in Plymouth to find out how a waterside amphitheatre and an urban beach are helping residents feel safer and more connected to one another.

Producer: Marijke Peters Presenter: Marnie Chesterton

Editor: Richard Collings Production Coordinator: Jonathan Harris

Contributors:

Dr Frances Hopkins, Plymouth Marine Laboratory Dr Mike Moore, Plymouth Marine Laboratory Dr Mathew White, University of Vienna Dr Easkey Britton

Image credit: David Sacks | The Image Bank | Getty Images | 164241179

Created for the #BBCWorldService.

Lazy. Unmotivated. Procrastinating. If those are words you?re used to hearing from your inner critic, you are not alone. Take CrowdScience listener Laurie. On her days off she loves to relax on the sofa, watch TV, put off chores and generally do as little as possible. Meanwhile she sees other family members and colleagues apparently buzzing with energy: going the extra mile at work, taking up hobbies, going to the gym. Why, she asks, is she so lazy?

CrowdScience turns to experts to find out whether or not so-called ?laziness? is a fundamental part of biology or psychology; why some people have more energy than others; and we offer a few tips for boosting energy and motivation. Or maybe Laurie is just being a bit too hard on herself?

With psychologists Professor Fuschia Sirois and Dr Devon Price, anthropologist Professor Herman Pontzer and start-up entrepreneur Akhil Aryan.

Presented by Dr Alex Lathbridge Produced by Cathy Edwards for the BBC World Service Editor: Richard Collings Production Co-ordinator: Jonathan Harris Studio Manager: Jackie Margerum

Image: Asleep under a book (Credit: RichVintage via Getty Images)

Meet the ostrich, one of nature?s most unusual creatures: a two-metre-tall, flightless bird that struts about the African savannah. CrowdScience listener Pat found herself entranced by seeing them on a wildlife documentary, where two ostriches were exhibiting some bizarre behaviour. According to her, the female was sitting on her eggs in a ?nest? that was barely a dent in the ground, while the male was just flapping his feathers around her. So Pat came to us to ask: what are ostriches for? Anand Jagatia starts by meeting one face-to-face at Woburn Safari Park. Tom Robson, Head of Reserves at the park, gives Anand a tour of ostriches? unique features. He discusses their status as the largest and fastest birds in the world and explains the unusual mating behaviour Pat observed on the TV programme she was watching. Next, to answer why some of these traits exist, Peter Houde from New Mexico State University dives into the ancient fossils. Peter is one of the palaeontologists who has managed to uncover the secrets of ostrich origins. What did their ancestors look like -- and why did they lose the ability to fly? Ostriches are also a part of human culture. Their eggs, for example, have been objects of value for thousands of years. Archaeologist Tamar Hodos from the University of Bristol explains how decorated ostrich eggs have been uncovered from ancient tombs and how they were probably used as pouring vessels as well as status symbols.

Anand receives an ostrich egg in the post and manages to cook it using a very specific and British process. Finally, designer Pascale Theron tells us about the history of the ostrich farming industry. It?s a classic rags-to-riches-to-rags tale, a manic boom at the start of the 20th Century all based around feathers that were worth their weight in gold. Presenter: Anand Jagatia Producer: Phil Sansom

Editor: Richard Collings

Production Co-ordinator: Jonathan Harris

Image credit: Phil Sansom & Anand Jagatia