- > Screens can be a lifeline
- > Positive and negative effects of screen time
- > Screen time effect on academic grades
- > Establish screen time rules for the whole family
- > Introduce frequent screen breaks
- > Apps to limit screen time for kids
- > Addiction dangers of too much screen time early in life
- > Dangers of childhood computer gaming
- > Screen time effects on educational development
- > Tablets before bedtime cause sleep disruption
Many parents are under the belief that technology and gadgets are essential for a child's development, but can you go too far? How much time should a child spend in front of a screen is a question being asked not just by worried parents but psychologists, health organisations and even governments. Here, you can read a collection of experts' guidelines for managing a child's screen time, and their warnings and advice on the dangers of recreational screen time, especially before bedtime. (Also see: Is YouTube safe for kids?)
Isolation update: Screens can be a lifeline
This is especially pertinent today where families are having to avoid usual social contact. Social distancing and self-isolation at home have resulted in nearly a two-fold surge of children’s smartphone screen time, according to Bosco, a monitoring app for the online and social activity of children and teens.
At the end of February, average mobile phone usage was 4:30 hours a day. After schools closed, it spiked to about six hours and now reaches an average of 8:40 hours. The number of messages in the WhatsApp groups of children is now 5 times higher, and as for teens aged 13 and over it is now 7.5 times higher than before the Coronavirus crisis started, reports Bosco.
A Harris Poll survey in August found nearly seven in 10 parents of 5-to-17-year-olds said their kids’ screen time had increased, and 60% felt they “have no choice but to allow it.”
Children are averaging an extra 1.5 hours of screen time a day on school days, not counting usage for school.
The British Psychological Society warns that “Too much screen time for young children can unintentionally cause permanent damage to their still-developing brains. The ability to focus, to concentrate, to lend attention, to sense other people’s attitudes and communicate with them, to build a large vocabulary - all those abilities are harmed.”
However, child psychologists are now warning that months of isolation are likely to have serious emotional consequences to children, especially an only child.
Penelope Leach, author of the bestselling Your Baby and Child, previously said it would be best for children under two not to have any screen time at all, but now recognises that “we are in a completely different situation”. “Screens do not entirely replace face-to-face interaction, but it is better than nothing,” she advises, suggesting applications such as WhatsApp, Zoom and Houseparty to talk online to friends.
The US Department of Health and Human Services estimates that American children spend a whopping seven hours a day in front of electronic media.
The UK government's Commons Science & Technology Committee has announced an inquiry into the impact of social media and screen-use on young people's health. And Unicef has published a review on the effects of digital technology on children's psychological wellbeing, including happiness, mental health and social life. This suggested that some screen time could be good for children's mental wellbeing, but that too much had a negative impact.
The UK's Royal College of Paediatrics and Child Health (RCPCH) does not set time limits for different age groups because there's a lack of evidence. The World Health Organization (WHO) advises that screen time should be replaced with more time for interaction, physical activity and sleep.
In the US and UK the average age for kids getting a phone is 10.
Positive and negative effects of screen time
Here we look at the positive and negative effects of screen time, and how it can affect academic results and even lead to non-screen addictions later in life. We look at establishing rules for children, and how we need to follow these ourselves as parents. Screen breaks are important, and there are apps that can help you reduce screen time.
There's a lot of detail here, so if you just want to know some quick guidelines, read our shorter Parents and Children’s Screen Time guidelines at the end of this feature.
The reason behind all this gadget use: over a third of parents (35 percent) said they use tech gadgets to entertain their children because they are convenient, and nearly a quarter (23 percent) because they want their children to be tech-savvy. A 2015 survey of 1,000 British mothers of children aged 2 to 12 found that 85 percent of mums admit to using technology to keep the kids occupied while they get on with other activities. The AO.com survey pointed to children spending on average around 17 hours a week in front of a screen – almost double the 8.8 weekly hours spent playing outside.
Wanting our children to be tech-savvy is understandable, and the need to keep them entertained (while we work or just tidy up after them!) will also make sense to many a parent. But we must also weigh up the risks associated with children having too much screen time.
In his lecture ‘Managing Screen Time and Screen Dependency’ Dr Aric Sigman argues that “whether it’s Facebook, the internet or computer games, screen time is no longer merely a cultural issue about how children spend their leisure time, nor is it confined to concern over the educational value or inappropriate content – it’s a medical issue”.
Sigman is concerned less with a child’s ICT or Computer Science study or use of computers for homework, but more with their screen time in non-educational environments in front of entertainment screen media such as television, the internet and computer games. He has some strong recommendations for reducing children's screen time, from toddlers to teenagers – and adults, too.
Obviously he is less worried by educational television programmes and even some educational computer games or mobile apps, but still recommends strictly limiting all screen time for kids.
TV has been an easy "babysitter" for years now, aided even further with DVDs, Netflix and so on. But computer, tablet and mobile screens engender more worry, in what has been put down as merely the latest generational complaint – "fresh expressions of horrible and timeless anxieties ... a tried and true form of advanced-age self-care".
The current generation of children in most Western societies spends more time in front of a screen than any before it. A study back in 2010 – before even the phenomenal rise of Apple’s iPad and other tablets – estimated that by the age of 10 children had access to an average of five screens in their lives. That number, Sigman suggests, has almost certainly risen since.
In addition to the main family TV, for example, many young children have their own bedroom telly along with portable computer game consoles (Nintendo, PlayStation, Xbox), smartphone, family computer and a laptop and/or a tablet computer.
By the age of seven the average child will have spent a full year of 24-hour days watching recreational screen media, claims Sigman. Over the course of childhood, children spend more time watching TV than they spend in school.
More screens means more consumption, and more medical problems argues Dr Sigman.
Screen time effect on academic grades
In 2015 Cambridge University researchers recorded the activities of more than 800 14-year-olds and analysed their GCSE results at 16. Those spending an extra hour a day on screens (TV, computer, games console, phone) saw a fall in GCSE results equivalent to two grades overall.
On average, the 14-year-olds said they spent four hours of their leisure time each day watching TV or in front of a computer.
An additional hour of screen-time each day was associated with 9.3 fewer GCSE points at 16 - the equivalent of dropping a grade in two subjects. Two extra hours of screen-time was associated with 18 fewer points - or dropping a grade in four subjects. Even if pupils spent more time studying, more time spent watching TV or online, still harmed their results, the analysis suggested.
Establish screen time rules for the whole family
So how much screen time is healthy for a 7 year-old, 10 year old, even 1, 2 or 3 year old? How much TV should a child watch? How many hours in front of a computer? You may be be shocked at too how much time in front of a screen has an adverse effect on a child's health and development.
Parents who want to reduce their children’s screen time need to establish rules to reduce the risk of later health and psychological issues.
Sigman admits that there is a lack of clarity of advice, but points to a number of governmental advice points on the maximum amount of time a child should spend in front of a screen.
In 2013 the US Department of Health recommended that children under two years of age should not be in front of a screen at all, and over that age the maximum leisure screen time should be no more than two hours a day.
The French government has even banned digital terrestrial TV aimed at all children under three, while Australia and Canada have similar recommendations and guidelines.
Harvard clinical psychologist and school consultant, Catherine Steiner-Adair (author of The Big Disconnect: Protecting Childhood and Family Relationships in the Digital Age) has studied the impact of digital technology on infant brain development. A baby's brain is hardwired to learn language, emotions and how to regulate them. Steiner believes there is no productive role technology can play in the life of a baby under two years.
Taiwanese parents are now legally obligated to monitor their children’s screen time. The Taiwanese government can levy £1,000 fines on parents of children under the age of 18 who are using electronic devices for extended periods of times. Similar measures exist in China and South Korea that aims to limit screen time to a healthy level.
The UK government has recently backtracked on a 2008 guidance that children should be exposed to technology and computers from a very young age, but there is currently no medical or governmental guidelines on screen time in the UK. The advice from the National Institute for Health and Care Excellence (Nice) is that children should have TV-free days, or have two-hour limits on the time spent in front of screens.
Ofcom in the UK estimates that the average 3-4-year-old spends three hours a day in front of a screen. This rises to four hours for ages 5-7, 4.5 hours by ages 8-11, and 6.5 hours for teenagers.
The report also found that older children are spending more time online and are more likely to go online alone, children aged 12-15 are spending more time online (rising from 14.9 hours a week to 17.1 hours) and spend as much time in a week using the internet as they do watching television. Up to 43 percent of kids are also more likely to mostly use the internet in their bedrooms.
Children who use the internet mostly alone comprise one in seven internet users aged 5-7 (14%), one in four aged 8-11 (24%) and over half of those aged 12-15 (55%).
Children are going online via a wider range of devices. Internet access using a PC or laptop is increasingly being supplemented by access through other devices. All age groups are more likely in 2012 to go online using a tablet computer, and children aged 5-7 and 12-15 are also more likely to go online using a mobile phone.
It's telling that Apple's Steve Jobs didn't allow his kids to play with iPads at all. Steve was a bit of an extremist, but limiting screen time should be at the front of every parent's mind – and that includes their own screen time in front of children. And Bill Gates of Microsoft capped video-game time for his daughter.
Steiner-Adair found that babies showed signs of distress when they looked to a parent for a reassuring connection and discovered the parent is distracted by technology. Her research found that 70 percent of kids think their parents spend too much time on devices, and accuse their parents of double standards.
Two of Apple's largest shareholders recently called on the tech giant to develop software that limits how long children can use its smartphones.
Parents know that to establish rules for their children they need to be roles models too. So that means putting your phone down when around the kids, and trying not to eat every meal in front of the TV. You can't lecture a child about screen time if you are getting too much too!
We should look out for “technology-based interruptions in parent-child interactions” – a phenomenon known as “technoference”, which seems to correlate with children being more prone to whining, sulking, restlessness, frustration and outbursts of temper.
Introduce frequent screen breaks
Dr Larry Rosen, psychology professor at California State University, says that it's more important to limit the stretches of time children spend in front of screens rather than worry about the total amount each day. Frequent breaks stop the brains from becoming over stimulated and combat screen addiction. Kids need to switch off without stress.
Rosen suggests a limit of 40 minutes then an hour's break for under 10s. For older pre-teens that should be a maximum of an hour, then an hour off. For teenagers it should be a maximum of an hour and a half.
Give kids a five-minute warning before their allotted time is up, and take away future screen time if they don't switch off. You can give bonuses for good screen behaviour but be aware that this goes against the overall message of moderation so use it sparingly.
Apps to limit screen time for kids
There a few apps that parents can install to actually limit the time their children spend on a computer and/or mobile screen.
British-based ScreenLimit is the only cross-platform/device (iOS, Android, Amazon Kindle Fire, and Windows) solution that we've seen. ScreenLimit lets parents remotely manage their children's screen time from a smartphone, tablet or web browser. Each child has a daily time limit (shown via a countdown) that allows them to switch between multiple devices on the same timer ensuring that they can't use more screen time than they've been allocated. Read more in our Best Parental Control Software round up.
Using ScreenLimit children can also earn extra screen time by completing set tasks (eg. brushing teeth, cleaning room, making bed, etc) as well as being penalised for less happy events. Devices and apps can be blocked with one click. Educational apps and websites can be whitelisted so they don't use up the child's precious screen time allocation. ScreenLimit is currently in beta version but can be downloaded now; you can try it for free for 1,000 active minutes, and later buy for £2.99/month or an annual or lifetime price. One subscription for a family covers up to 10 children on unlimited devices. More details at ScreenLimit.
The Monqi kids smartphone is designed to give parents the chance to see what their child is up to.
Addiction dangers of too much screen time early in life
“Early screen viewing is likely to lead to long periods of viewing for the rest of your life," says Sigman. "The way you view screens when you are young forms the habits you pick up for ever after it seems.”
An early taste for entertainment screen media can lead to changes in the brain that stay with you for life – a life that may be shorter as a result.
Like other addictions screen time creates significant changes in brain chemistry – most notably, in the release of dopamine. This neurotransmitter – also known as the pleasure chemical – is central to addictions from sugar to cocaine. Dr. Peter Whybrow, director of neuroscience at UCLA, calls screens “electronic cocaine” and in China researchers tag them “digital heroin.”
"Dopamine is produced when we see something that is interesting or new, but it also has a second function. Dopamine is also the neurochemical involved in most addictions – it's the reward chemical.
"There are concerns among neuroscientists that this dopamine being produced every single day for many years – through for example playing computer games – may change the reward circuitry in a child's brain and make them more dependent on screen media," warns Sigman.
(If you want to see some head-scratchingly weighty, early scientific research on computer games and dopamine release, check out this 1998 research paper from the Division of Neuroscience and Psychological Medicine, Imperial College School of Medicine.)
In her study of “Internet Addiction” by Dr. Kimberly Young suggests that 18 percent of college-age internet users in the US suffer from tech addiction.
On the perils of too much screen time Sigman has investigated the extent to which time online may be displacing face-to-face contact, and that lack of social connection is associated with physiological changes, increased incidence of illness and higher premature mortality.
Dangers of childhood computer gaming
Think about the type of games children are getting addicted to playing. The narrative of a game is an important factor, as some – Grand Theft Auto being the obvious example – clearly lead to a lack of impulse control, and potential neuro-chemical changes in the release of dopamine.
"Providing a child with a lot of novelty may produce higher levels of dopamine in a child's brain, making the child seek more and more screen time to satisfy their need for more dopamine,” says Sigman.
An article in the American Journal of Drug and Alcohol Abuse suggested that “computer game playing may lead to long-term changes in the reward circuitry that resemble the effects of substance dependence”.
“Computer game addicts or gamblers show reduced dopamine response to stimuli associated with their addiction presumably due to sensitization.”
However, an Oxford University team instead found a link between people who spent time gaming each week with those who had a positive sense of wellbeing.
“Play can be an activity that relates positively to people’s mental health - and regulating video games could withhold those benefits from players,” Andrew Przybylski, director of research at the Oxford Internet Institute, said.
Another recent report from the University of Montreal found that while social media use, TV viewing and computer use was linked to anxiety, video gaming was not and could make teenagers happier.
Games in a virtual world also lead to a false sense of competence. Children need to base their lives on reality not fake, virtual worlds, says Sigman.
Sigman is also sceptical about the supposed benefits of computer game play, such as better hand-eye co-ordination. There may well be improved eye-hand-keyboard-mouse dexterity but many reports of such benefits are sponsored by interested games and tech companies, he claims.
Fast use of a games console controller is of little use outside of the gaming environment. And the reduction in sustained attention is a far greater loss.
On the other hand Robert Hannigan, the former head of the UK Government’s electronic spy agency, says that parents fear an online world where they understand less than their children: “Parental guilt is driven by a failure to appreciate that life online and ‘real’ life are not separate: they are all part of the same experience. Millennials understand this. Gaming and social media can be as sociable as mooching around the streets with a group of friends was once.”
Catherine Steiner-Adair, a clinical psychologist and author of ‘The Big Disconnect: Protecting Childhood and Family Relationships in the Digital Age’, disagrees that increased screen time is good for children and young adults. Children who are heavy users of electronics may become adept at multitasking, she argues, but they lose the ability to focus on what is most important – a trait critical to the deep thought and problem solving needed in life.
Screen time effects on educational development
Children’s cognitive development is two years down on what it was 30 years ago because children have lost both concrete and abstract thinking.
Today’s children have less idea of weight and length measurements because the more time spent in virtual worlds, the less they are involved in the real world. This is the finding from two expert reports from 2007 and 2009: 'Thirty years on - a large anti-Flynn effect? The Piagetian test Volume & Heaviness norms' by Michael Shayer and Denise Ginsburg.
Sigman is critical of schools over-use of technology, which he blames on the multi-billion-pound education-tech industry forcing its products on schools and even nurseries on the unfounded fear that children suffer without using the latest digital devices.
“Until we know better, I advise precaution,” says Sigman. “Keep technology and screens away from the under threes, and set limits on all ages after that.”
A study conducted in 2017 by the Center on Media and Child Health and the University of Alberta found that 75% of teachers surveyed say students’ ability to focus on educational tasks has decreased.
With so many dangers associated with too much screen time for children, and little fixed advice from health authorities or governments Dr Sigman offers his own guidelines (see below) for reducing the risks.
Keep reading for our handy screen-time tips for parents on the next page...
Tablets before bedtime cause sleep disruption
Sigman was recently interviewed on British TV – watch the clip here – about how the use of tablets and other electronic devices can disrupt children’s sleep – indeed adults’ sleep will also be affected by what is known as “Blue Light” that these tech products emit.
The light from digital devices is “short-wavelength-enriched,” so it has a higher concentration of blue light than natural light – and blue light affects levels of the sleep-inducing hormone melatonin more than any other wavelength.
“Recreational screen time has now moved in to the bedroom,” warned Sigman.
“There is a strong link between tablet or any type of small screen that emits what is known as ‘blue light’ – good in the morning as it wakes us up; bad in the night as it wakes us up.
“The Kindle Paperwhite doesn’t emit the same levels of blue light. And there are filter glasses and apps that actually change the type of light, but light isn’t the only reason.
“Brains are being stimulated before bedtime in the way that books don’t do. Exciting games just before bedtime is not a good idea. Electronic devices should be switched off at least an hour before bedtime,” the expert warns.
It’s not necessarily all bad
Experts who regard some screen time as beneficial urge parents to pay attention to how their kids act during and after watching TV, playing video games, or on the computer online. “If they're using high-quality, age-appropriate media, their behaviour is positive, and their screen-time activities are balanced with plenty of healthy screen-free ones, there's no need to worry.”
But even these parents should consider creating a schedule that works for their family: including weekly screen-time limits, limits on the kinds of screens they can use, and guidelines on the types of activities they can do or programmes they can watch. See our guidelines below.
It’s important to get your kids' input as well – media literacy and self-regulation help buy in. It’s also a great opportunity to discover what your kids like watching, letting you introduce new shows and apps for them to try.
So how much screen time for children?
The simple answer: not much. None for children under two. That’s right. The experts suggest that babies and toddlers are kept away from all screens. Sorry CBeebies.
Children aged 2-5 years should have no more than an hour a day, and children aged 5-18 years should have no more than two hours a day. That's a tough call for teenagers, especially with homework often requiring computer time. But remember that the real danger is non-educational, leisure screen time, so you may wish to discount homework screen time.
Parents should be able to decide if these strictures are too harsh, and allow some screen time flexibility, but not caring at all about the amount of time your children spend in front of screens is dangerous.
Parents and Children’s Screen Time guidelines
Minimise screen time for children under three. The French government recommends no screen time in this age group. A maximum of two hours leisure screen time for children aged over 3. This does not include homework.
Check access and availability
Don’t allow TVs, computers or any screen-based device into a child’s bedroom. Sigman relates that he has spoken to many parents who have regretted allowing screens into bedrooms and feel removing them later is harder than refusing them in the first place. Even though it may be difficult, you should take the screens away from the bedroom. Otherwise you risk your child’s cognitive and physical health.
Most parents haven’t devised screen-time protocols for their children, and need to create media-free zones in their homes, banish TV dinners, and put away their own digital devices when communicating with their children, he urges.
Explain the reasons
Don’t just switch off the telly, tablet or computer – explain to your child why you are limiting screen time. Discuss the health benefits of reduced screen time. Children will listen to the health reasons for reduced screen time if the dangers are clearly pointed out.
Sigman debunks the notions that children who have little screen time will be less likely to learn as much as those who do enjoy unlimited time in front of computers or the TV. They also won’t rebel later in life.
Technology is a tool for learning, not the end in its own right.
Parental role modelling
Ever catch yourself checking your email, using your smartphone or watching TV while your child is trying to talk to you? Stop using the device and communicate with your child face to face. This will help establish empathy and also set a good example of the child.
The parent is a child’s primary role model, and sticking the kids in front of a screen is an example of what is known as benign neglect.
Don’t have all meals in front of the TV, and don’t keep reaching for your smartphone while in front of the child. It tells the child that constant screen time is acceptable. And it will do you good, too!
Engage in their world
Spend some time with your child online - look at the sites, games or YouTube videos they are watching. You need to understand your child's online life.
Mums need to nag
It might sound sexist but Dr Sigman claims that a mother’s nagging – “maternal monitoring” in nicer terms – is the best way to get children to change their behaviour. Dads need to enforce the rules, too.
Remove background noise
You may not realise it but passive viewing is ruining your child’s concentration. A child’s attention will wander if you’re watching the TV news in another part of the room.
Take an average week and look at how much screen time your child, and indeed the whole family, is subjecting themselves to. Add up the favourite TV shows, smartphone and tablet app play, Internet browsing and video games, and that two hours is filled up very quickly.
Screen time often leads to over stimulation so take breaks to calm down a child’s brain. See our time guidelines earlier in this feature.
Multitasking is for adults, not children. Deep concentration in kids will lead to better, more creative thinkers. Research suggests that trying to get children to multitask actually makes them worse at multitasking because they don’t learn effective concentration skills.
No screens before bedtime
Take a gap between screen time and sleep. Most screens these days use LCDs that emit a blue light that inhibits sleep and disrupts the circadian rhythm (body clock). Remember that the bedroom is not an entertainment centre. It’s the place children go to sleep.
Create a boredom-buster list
To help children access their creativity and self determination get them to create a list of the sorts of things they'd like to do when not allowed to go to a screen. Stick the list on the fridge. Then when the child complains they have nothing to do you can refer them to the list, or add more to it.
Use screens to combat screen time
Use the wealth of the Internet to help you wean your kids off the screen. There are plenty of art projects online, cooking tips, gardening, science experiments... you name it there's plenty of online tutorials that should translate into time away from the screen.
If isolated, use screens to keep children social
We're not talking Facebook here, but applications such as WhatApp, Zoom and Houseparty allow kids to talk online to friends, which is really important if families are isolating for health reasons.
Alternatives to screen time
Dr Sigman is a big believer in what he calls the “gift of boredom”. He rubbishes the idea that the worst thing that can happen to a child is for he or she to be bored. Children, he says, need to learn how to deal with boredom. Being over stimulated is worse than being bored. Learning to cope with being bored leads to greater self sufficiency, and less risk that children later become addicted to unhealthy activities to fill such gaps.
Physical activity. Screen time is usually sedentary so getting the child up and moving is by far the healthier option. The latest scientific research actually suggests that screen-time sitting is worse for one’s health than standard sitting because of the over-stimulation that screen time induces in the user.
Being fitter, however, does not take away the harmful effects of screen time. Even keep-fit enthusiasts suffer ill effects of spending too much time sitting down.
The Journal of the American College of Cardiology ran a study in Scotland that found that “recreational sitting, as reflected by television/screen viewing time, is related to raised mortality and cardiovascular disease risk regardless of physical activity participation.”
Increased physical activity is, of course, beneficial but it doesn’t mean you won’t suffer an increased risk of death from over-doing your screen time.
So reduce hours of screen time by replacing with more physical activity, not just getting fitter while still spending too much time in front of the telly, computer or games console.
Hours of sedentary behaviour is linked not only to obesity, but other health problems such as type 2 diabetes, cardiovascular disease and stroke. While you’re thinking of how much time your kid is sitting down in front of a screen, do yourself a favour and have a walk about yourself.
Get outside. Suggesting going for a walk isn't going to cut it, so make the activity fun: tree climbing, hide-and-seek in a wood, or camping.
Social activity. Don’t fool yourself that being on Facebook all day is social. It’s vital that kids get out and interact with other children in real life and not in phony virtual worlds.
Hobbies. It might not feel like it sometimes but children are very good at working out ways of filling their time when they have to, and finding out some stimulating hobbies – art, craft, fishing, sports, Lego, kites, collecting, bird watching, astronomy, cooking, museums, photography, music, gardening, etc – shouldn’t be too difficult.
Do the chores. You're kidding, right? But kids should help out round the house, tidy up after themselves, learn some basic cooking, lay the table, empty the dishwasher, hang out the clothes... It might be boring but it does create a break from the screen.
Also: Best headphones for kids - keep your child's hearing safe with these kid-friendly headphones.
About Dr Aric Sigman
A Fellow of the Royal Society of Medicine Dr Aric Sigman has a Bachelor of Science (Honours) degree in Psychology, a Master of Science degree in The Neurophysiological Basis of Behaviour, and a Ph.D. in the field of the role of attention in autonomic nervous system self-regulation.
The British Medical Association British Medical Journals’ Archives of Disease in Childhood has recently published his paper on screen time as its leading article. Dr Sigman has addressed the European Parliament Working Group on the Quality of Childhood in the European Union, in Brussels, on the impact of electronic media and screen dependency. In 2012, the EU Parliamentary Working Group published his report on the impact of electronic media and screen dependency. Dr Sigman's previous books include The Spoilt Generation and Remotely Controlled: How Television is Damaging Our Lives.
He has published other papers, including Well Connected?: The Biological Implications of 'Social Networking', is published in The Biologist, Vol 56(1), the journal of the Society of Biology.?
His previous paper Visual Voodoo, on the biological effects associated with watching television, also published in The Biologist, and his talk at the Houses of Parliament, caused widespread public debate.