More or Less

Dr Spock’s dangerous advice on baby sleep

Sometimes it is obvious to everyone when an idea is harmful, or a piece of advice is damaging. But not always. Occasionally bad ideas and terrible advice end up being accepted in society and supported by people in authority. In such circumstances, one of the most powerful tools for changing people's minds is evidence – scientific studies that show beyond doubt that the bad idea is, indeed, a bad idea. That's the subject of a new book by Helen Pearson, titled Beyond Belief: How Evidence Shows What Really Works. An editor at the scientific journal Nature in her day job, the book chronicles those determined individuals who shake up the status quo by gathering just the right kind of evidence. One story in that book stood out to us on More or Less as it shows just what happens when you don't have the evidence you need to challenge a dangerous way of doing things. It's the story of a piece of advice from childcare expert Dr Benjamin Spock. In a 1958 revision of his bestselling parenting guide Baby and Childcare he made a small change to his advice on sleeping position – advising parents to put their babies to sleep on their front. It eventually became clear that this sleeping position was associated with a significant increase in the risk of sudden infant death, or cot death. CREDITS: Presenter: Charlotte McDonald Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound mix: Rod Farquhar Editor: Richard Vadon

How likely is ‘likely’?

When you’re listening to the news, you will often hear words that are meant to communicate the probability of something happening.   A terrorist attack is “a realistic possibility”, the spread of a certain strain of virus is “highly likely", the relegation of your favourite football team is “possible”. But when you hear these terms, do you really know what kind of probabilities they’re trying to convey? Do you know how likely “likely” is? Or what probability “probable” is meant to get across? In some cases, it seems you probably don't. Professor Adam Kucharski, author of Proof, the Uncertain Science of Certainty, designed a quiz to work out the actual probabilities of the language we use to convey risks. The data he got back shows how sometimes these words mean very different things to different people. If you want to try the quiz for yourself, head over to https://probability.kucharski.io/ Email the More or Less team: moreorless@bbc.co.uk CREDITS: Presenter: Charlotte McDonald Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound mix: Gareth Jones Editor: Richard Vadon

How much water does AI consume?

As Artificial Intelligence continues to expand rapidly, some people have raised concerns about its potential environmental impact - in particular its use of water, which is used to cool both data centres and the power generators that supply them with electricity. One recent book on AI contained the alarming prediction that AI could consume between 4 and 6 trillion litres a year by 2027. Could this eye-popping figure be right? If not, what is the correct figure, and is it a big number? The devil, as ever, is in the detail, and with the help of expert Alex de Vries-Gao, the More or Loss team has taken a deep dive to get to the truth about AI and water consumption. If you’ve seen a number in the news and you think More or Less should take a look, email the team on moreorless@bbc.co.uk Presenter: Charlotte McDonald Producer / Reporter: Nathan Gower Series Producer: Tom Colls Programme Coordinator: Brenda Brown Sound Mix: Dave O’Neil Editor: Richard Vadon

Paul Ehrlich: The man who bet England wouldn’t exist by the year 2000

Paul Ehrlich’s bestselling book The Population Bomb opens with an apocalyptic paragraph. “The battle to feed all of humanity is over,” it states. “In the 1970s and 1980s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date nothing can prevent a substantial increase in the world death rate.” Professor Ehrlich, who died last week, made a simple argument. The global population was outrunning our capacity to produce enough food to feed everyone. Famine, disease and nuclear Armageddon would follow if the population was not controlled. The book made him a celebrity, and he regularly spoke in public, warning of the imminent threat to humanity. Sometimes his warnings were quite vague in terms of the timescale, but other times not - he was reported as saying in 1968 that if current trends continued, by the year 2000, the UK would be a “small group of impoverished islands, inhabited by some 70 million hungry people". "If I were a gambler," he was quoted as saying, "I would take even money that England will not exist in the year 2000". But the UK did not collapse, the global death rate did not increase, and we have more food per person now than when he wrote the book. So, what went wrong with Paul Ehrlich's predictions of a population apocalypse? If you’ve seen a number or claim that you think More or Less should look at, email moreorless@bbc.co.uk CONTRIBUTORS Vincent Geloso, Assistant Professor of economics at George Mason University Darrell Bricker, global CEO of Ipsos Public Affairs and co-author of Empty Planet, the Shock of Global Population Decline Peter Alexander, Professor of Global Food Systems at the University of Edinburgh CREDITS: Presenter: Charlotte McDonald Series producer: Tom Colls Production co-ordinator: Brenda Brown Sound mix: Dave O’Neil Editor: Richard Vadon

Transgender women in sport: Does ‘comparable’ mean ‘equal’?

In most sports, men compete against men and women compete against women. That is generally considered fair, because men are faster, more powerful and have greater endurance. But there is an ongoing controversy about transgender women - people who were born male and now identify as women. Is it fair for them to compete in the women’s sport category or do they have an advantage? A study in the British Journal of Sports Medicine recently added to the debate with an analysis that found the strength and fitness of transgender women is “comparable” with that of women. More or Less looks into the research to explain what it does, and does not, say. Contributors: Professor Alun Williams, Manchester Metropolitan University Credits: Presenter: Charlotte McDonald Reporter: Tom Colls Production co-ordinator: Brenda Brown Sound Mix: Gareth Jones Editor: Richard Vadon