Why are more and more people giving up all food produced from animals? Mary-Ann Ochota explores if it’s natural for us to eat meat, and the impact on our health and the environment. She looks at how social media is helping spread the vegan message, the pros and cons of a solely plant based diet and whether eating meat today is ethical.(Image: Selection of Vegan dishes, Credit: Shutterstock)

Why do some sleep disorders turn normal dreams into terrifying nightmares? And what do they tell us about the workings of the brain? Dreaming usually occurs in REM sleep (Rapid Eye Movement sleep) when our brains are very active, but our bodies are almost completely paralysed. But sometimes, the switch that paralyses our muscles is faulty, causing conditions that can significantly impact our days and nights. Neurologist, Dr Guy Leschziner, from Guy's and St Thomas' hospitals in London, introduces us to some of his patients with problems that include sleep paralysis and hallucinations. We meet Evelyn whose sleep has been plagued by visions so scary, she doesn’t want to go to bed; we hear from Christian who has narcolepsy, a rare brain condition that makes him suddenly fall asleep at inappropriate times. And we meet John who has REM sleep behaviour disorder (known as RBD) which causes him violently to act out his dreams, sometimes injuring himself and his wife, Liz. And we learn how RBD may be an early warning of degenerative brain conditions like Parkinson's disease and certain types of dementia. These disorders arising from dreaming sleep help us to understand why we dream and the role of REM sleep.(Photo: Sleeping woman having nightmare, Credit: Getty Images)

Why high levels of noise affects all of us. David Baker explores how different sounds can impact on people without them even knowing and how to make our lives more tranquil. From the clangs and clatter of city life to weapons that use sound to harm us, noise can be a lot more dangerous than we think. But help is at hand from quieter underground stations to restaurants where the sound changes to reflect our moods and preferences.(Image: Crowded, noisy, station; Credit: Shutterstock)

Meet Rachel Waddingham and meet the voices that inhabit Rachel’s head: there is three-year-old Blue who just wants to play with other children, 11-year-old Elfie who is easily offended and a panel of three critical scientists. Peter hears a voice that dictated an entire children’s book to him. Around 2% of people claim, like Rachel, to be inhabited by voices with whom they have full blown relationships. Are they all sick? What causes people to hear voices? And why have some psychologists changed their minds about the dangers of colluding with the voices?(Photo: Rachel Waddingham)

Why do some of us do bizarre things in our sleep? Like riding a motorbike, using a shoe to ‘phone for pizza or even having sex while sleeping? These are complex behaviours and yet sleepwalkers aren’t aware of what they’re doing and often have no memory of their strange night-time activities. These sleep disorders are known as non-REM parasomnias and include conditions like night terrors and sleep eating. Neurologist, Dr Guy Leschziner, talks to patients he’s been treating at his sleep clinic at Guy’s and St Thomas’ hospitals in London. They include Jackie who began sleepwalking as a child and continued her strange night-time behaviour as an adult, even driving her car whilst sleeping; from Alex who rescues people from floods in his sleep. And we hear from Tom, whose recent diagnosis of sexsomnia has had a significant impact on his life.(Image: Girl on tightrope in moonlight, Credit: Shutterstock)

Catherine Carr asks why excessive drinking can sometimes seem to be socially acceptable. And why countries like America and India have at times turned against alcohol. She hears stories of addiction in India and Kenya and a history of temperance and prohibition movements in America. Medical specialists explain why people can become alcoholics, why some people are drinking more and the treatments available. How Alcoholics Anonymous began and how a new synthetic alcohol may provide a solution.(Image: People drinking, Credit: Shutterstock)

Why have so many women in so many different cultures and eras been denounced as witches? BBC Africa’s Sammy Awami visits a village in his home country of Tanzania where, just four months ago, five women were murdered after being accused of witchcraft. Sammy meets a witch doctor who believes he has met a witch and talks to a local politician who is trying to stop the killings. We also hear from Professor Dianne Purkiss, an expert on the European witch hunts of the Early Modern period. And he travels to Glastonbury in the South West of England to meets a modern-day witch, Liz Williams, owner of the Cat and Cauldron witchcraft shop.(Image: Villagers in N. Tanzania where people have been accused of being witches, Credit: Sammy Awami/BBC)

When a group of people come together, they form a crowd. Strangers connect and share a common purpose and identity. It's an exhilarating experience. At football matches, music festivals and protest marches, people become energised in groups. They can be frightening places when they erupt in violence, or peaceful forms of protest when we try to change social norms. In this edition of the Why Factor, Sandra Kanthal asks why we take courage from a crowd.(Image: Large crowd of people, Credit: Shutterstock)

Coming of age rituals, hazing at universities or entrance rites into secretive organisations, initiations are present in every culture around the world. They are often secretive and can involve horrific ordeals and yet people are still prepared to put up with the pain. So why do we need them and what happens if they are absent?Rhianna Dhillon talks to young men in South Africa who’s coming of age circumcisions went horribly wrong, learns about the inner workings of gang initiations and the mysterious rites held by the elite Skull and Bones organisation. She discovers that however harmful the initiation ceremony, it almost always serves a valuable purpose.Image: People holding hands around a fire, Credit: Getty Images

Professor James Tilley finds out what we can learn about politics from the power struggles within chimpanzee groups and how our evolutionary past affects the political decisions that we make today. Interviewing primatologists, evolutionary psychologists and political scientists, he explores the parallels between our political world and that of other primates. These include the way politicians form coalitions, how people choose leaders, loyalties to parties and even how, and when, we go to war. These similarities to other primates reflect our evolutionary heritage and the way in which stone-age human groups settled disputes internally and externally. (Photo: A female chimpanzee yawns as two others nod-off, while they sit on rocks in a family group, at Taronga Zoo, Sydney. Credit: Getty Images)