As someone who dislikes crowds, listener Graham is curious about them. Crowds gather in all sorts of places, from train stations and football matches, to religious events and protest marches. But is there a science behind how they move and behave? To find out, Anand Jagatia speaks to some actual crowd scientists.  He learns about the psychology of social identity, which influences everything from how close we stand to others to how we react in emergencies. He visits the Athens marathon, and hears about the algorithm that predicts how 50,000 runners will move through a city on race day. And he explores research into the science of riots, which explains why some peaceful crowds turn violent. Presented and produced by Anand Jagatia Contributors:
Dr Anne Templeton, University of Edinburgh
Marcel Altenburg, Manchester Metropolitan University
Prof John Drury, University of Sussex Archive: BBC News
Image: Crowd from above. Creidt: Getty Images

How do we behave in crowds?

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Mosquitoes are responsible for more human deaths than any other animal. These tiny creatures transmit many diseases, but the most devastating is malaria. It kills over half a million people every year, most of them children.  So why are people still dying of malaria in such large numbers, when so much time and money has been invested in trying to eradicate it? What do we know about mosquitoes and malaria, and what do we still need to learn? CrowdScience visits Malawi, one of the African countries leading the way against malaria, with the rollout of the world’s first malaria vaccine programme.  Presenter Caroline Steel is joined by a live audience and a panel of experts: Wongani Nygulu, Eggrey Aisha Kambewa and Steve Gowelo. Together they explore questions from our listeners in Malawi and around the world, like why female mosquitoes feed on blood while males drink nectar; why some people are more likely to be bitten by mosquitoes than others; and how we might modify the insects’ DNA to stop them spreading diseases.  About half a million children across Malawi have been vaccinated since 2019. We visit a clinic in nearby Chikwawa to meet the staff involved in the vaccination programme there, and the mothers embracing the opportunity to protect their babies against this deadly disease.  Recorded at Malawi Liverpool Wellcome Trust (MLW), Blantyre, Malawi.  Contributors: 
Dr. Wongani Nygulu, Epidemiologist, Malaria Alert Centre 
Eggrey Aisha Kambewa, MLW entomologist, MLW 
Dr. Steve Gowelo, University of California San Francisco Malaria Elimination Initiative  Presenter: Caroline Steel 
Producer: Jeremy Grange 
Researcher: Imaan Moin 
Additional Recording: Margaret Sessa Hawkins & Sophie Ormiston 
Editor: Cathy Edwards 
Production Co-ordinator: Liz Tuohy (Photo: A mosquito, that is silhouetted against the moon, bites a human arm. Credit: LWA/Getty Images)

Why are people still dying from malaria?

When CrowdScience listener Israel from Papua New Guinea received a bad grade on a maths test in third grade, he looked around the class and realised that almost all the other students had received a better result. Since then, he has always wondered: why are some people better at maths than others? 
 
And Israel isn’t the only one to think about this: our listeners from all over the world describe their relationships with numbers, which run the full gamut from love to hate.  
  
So are we all in control of our own mathematical fate, or are some people just naturally bad at it? Presenter Anand Jagatia hears about studies of identical and non-identical twins showing how genetics and environment interact to shape our mathematical abilities. 
  
Our numerical abilities are not set in stone. It’s always possible to improve, and getting rid of negative feelings and anxiety around maths could be the key, says psychologist Iro Xenidou-Dervou. 
 
Some countries seem to support children’s maths skills better than others. China and Finland both rank highly in international league tables; education experts in both countries discuss whether there are any keys to a successful mathematics education. 
  
And there is something underlying our ability to do maths in the first place: our number sense. We hear what happens when this number sense does not work as intended – and what can be done about it.  
  
Contributors: 
Professor Yulia Kovas – Goldsmiths University of London, UK 
Professor Pekka Räsänen – University of Turku, Finland 
Assistant Professor Zhenzhen Miao – Jiangxi Normal University, China 
Dr Iro Xenidou-Dervou – Loughborough University, UK 
Professor Brian Butterworth – University College London, UK 
 
Presented by Anand Jagatia 
Produced by Florian Bohr 
Editor: Cathy Edwards  
Production Co-ordinator: Liz Tuohy  
Studio Manager: Jackie Margerum  (Photo: Boy scratching head in front of blackboard. Credit: Jose Luis Pelaez Inc/Getty Images)

Why am I bad at maths?

Coastlines around the world are changing, causing serious problems for the many communities living near the sea, as well as vital and fragile coastal ecosystems.  In the second of a two-part special on coastal erosion, CrowdScience explores the best ways to tackle this problem. Presenter Caroline Steel visits the Caribbean island of Puerto Rico to see the various methods they use to protect their coasts.  First up: ‘riprap’ – rocks strategically placed to keep the encroaching sea at bay. The problem is, while it protects the area immediately behind the rocks, riprap can exacerbate erosion nearby.   But there are other, more nature-friendly solutions, including sand dune restoration. Caroline picks up her shovel and helps to re-plant dunes, destroyed in the past by erosion as well as sand extraction for the construction trade. The roots of these plants stabilise the dunes, while building boardwalks prevents further damage from humans.   Nature also offers the perfect offshore protection against coastal erosion: coral reefs. These are the first line of defence in absorbing the power of the ocean’s waves. Down on the beach, we see for ourselves just how effective they are. The reefs face threats, but restoration plans are afoot. We visit a nursery that grows corals to plant out on the reefs – and find out about corals’ surprising cannibalistic tendencies in the process.  Featuring: 
Professor Robert Mayer - Director of Vida Marina, Center for Conservation and Ecological Restoration, University of Puerto Rico 
Nada Nigaglioni - Biology student, University of Puerto Rico  
Ernesto Diaz - Caribbean Regional Manager at TetraTech 
Dr Stacey Williams - Executive Director, ISER Caribe  Presenter: Caroline Steel 
Producer: Hannah Fisher 
Editor: Cathy Edwards 
Production Co-ordinator: Liz Tuohy 
Studio Manager: Emma Harth (Photo: Coast restoration measures at Ultimo Trolley Beach, Puerto Rico. Credit: BBC)

How should we protect our coastlines?

Around the world, coastlines are constantly changing due to the power of waves, currents and tides. Coastal areas are also some of the most heavily populated and developed land areas in the world. So it’s not hard to see how the natural process of coastal erosion can cause serious problems for us.    It’s an issue that’s been bothering CrowdScience listener Anne in Miami Beach, Florida. She can see the beach from her window and wonders why after every storm, several trucks arrive to dump more sand on it.   In this first of two programmes, CrowdScience visits Anne’s home in south Florida and finds out how erosion threatens Florida’s famous beaches. Caroline Steel speaks to geoscientist Dr Tiffany Roberts Briggs and hears why it’s such a problem for this tourist-reliant state. Tiffany explains the delicate balance between natural processes and human infrastructure.   Meanwhile, the Caribbean island of Puerto Rico declared a state of emergency in April 2023 due to coastal erosion. Caroline witnesses the impacts of erosion first-hand, as Ruperto Chaparro shows her abandoned houses crumbling into the sea.   But how can we quantify the rate of erosion? Dr Kevian Perez in the Graduate School of Planning at University of Puerto Rico explains the methods they use to monitor Puerto Rico’s coastlines, and how they are evaluating the effectiveness of different mitigation methods.   However, some of the methods used to protect coastal communities from the encroaching sea have done more harm than good. So what are the best ways to tackle this problem? That’s what we’ll be exploring in next week’s programme.   Presenter: Caroline Steel 
Producer: Hannah Fisher 
Editor: Cathy Edwards 
Production Co-ordinator: Liz Tuohy  
Studio Manager: Steve Greenwood and Bob Nettles  Featuring: 
Dr Tiffany Roberts Briggs, Associate Professor at Florida Atlantic University 
Ruperto Chaparro, Director of Sea Grant Programme, University of Puerto Rico 
Anabela Fuentes Garcia, Villa Cristiana community leader 
Dr Kevian Perez, researcher at the Coastal Research and Planning Institute of Puerto Rico at the Graduate School of Planning (Photo: Puerto Rico after Hurricane Maria. Credit: Orlando Sentinel/Getty Images)

Are our coastlines being washed away?

How do we know where a sound is coming from?  Another chance to hear this ear-opening episode, exploring a question from CrowdScience listener Chiletso. One day, he heard his son bounce a ball and instantly knew the direction it was travelling. How?  Anand Jagatia sets out to discover what makes left, right, up and down sound so different.  First, he gets blindfolded, so Alan Archer-Boyd, former auditory scientist and lead engineer at BBC R&D;, can put his sound localisation skills to the test. It turns out that having two ears and pinnae, those flappy bits of cartilage on the side of your head, help a lot.  Professor Eric Knudsen shares how the barn owl’s asymmetrical ears allow it to hunt mice, even in complete darkness.  And Anand uncovers how far he can push his own spatial hearing. Blind activist and researcher Thomas Tajo teaches him how to echolocate like a bat, and Dr Lore Thaler explains what is going on in the brain of experienced echolocators.  This programme was originally broadcast in March 2023.  Presented by Anand Jagatia 
Produced by Florian Bohr for the BBC World Service  Image: Boy with hands at his ears 
Credit: Silke Woweries/Getty Images

How do we behave in crowds?

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