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Now you see it, now you don't: what optical illusions tell us about our brains

Illusions can offer insights into how the visual system processes images.

Maurits Escher: where do the staircases lead?

The human brain is a network of about 20 billion neurons – nerve cells – linked by several trillion connections. Not to mention glial cells, which scientists used to think were inactive scaffolding, but increasingly view as an essential part of how the brain works. Our brains give us movement, language, senses, memories, consciousness and personality. We know a lot more about the brain than we used to, but it still seems far too complicated for human understanding.

Fortunately, the brain contains many small networks of neurons that carry out some specific function: vision, hearing, movement. It makes sense to tackle these simple modules first. Moreover, we have good mathematical models of nerve cell behaviour. In 1952, Alan Hodgkin and Andrew Huxley wrote down the “Hodgkin-Huxley equations” for the transmission of a nerve impulse, which won them the 1963 Nobel Prize in Medicine. We also have effective techniques for understanding small networks’ components and how they are linked.

Many of these simple networks occur in the visual system. We used to think that the eye was like a camera, taking a “snapshot” of the outside world that was stored in the brain like a photo stuck in an album. It uses a lens to focus an image on to the retina at the back of the eye, which functions a bit like a roll of film – or, in today’s digital cameras, a charge-coupled device, storing an image pixel by pixel. But we now know that when the retina sends information to the brain’s visual cortex, the similarity to a camera ends.

Although we get a strong impression that what we are seeing is “out there” in front of us, what determines that perception resides inside our own heads. The brain decomposes images into simple pieces, works out what they are, “labels” them with that information, and reassembles them. When we see three sheep and two pigs in a field, we “know” which bits are sheep, which are pigs, and how many of each there are. If you try to program a computer to do that, you quickly realise how tricky the process is. Only very recently have computers been able to distinguish between faces, let alone sheep and pigs.

Probing the brain’s detailed activity is difficult. Rapid progress is being made, but it still takes a huge effort to get reliable information. But when science cannot observe something directly, it infers it, working indirectly. An effective way to infer how something functions is to see what it does when it goes wrong. It may be hard to understand a bridge while it stays up, but you can learn a lot about strength of materials when it collapses.

The visual system can “go wrong” in several interesting ways. Hallucinogenic drugs can change how neurons behave, producing dramatic images such as spinning spirals, which originate not in the eye, but in the brain. Some images even cause the brain to misinterpret what it’s seeing without outside help. We call them optical illusions.

One of the earliest was discovered in Renaissance Italy in the 16th century. Giambattista della Porta was the middle of three surviving sons of a wealthy merchant nobleman who became secretary to the Holy Roman emperor Charles V. The father was an intellectual, and Giambattista grew up in a house in Naples that hosted innumerable mathematicians, scientists, poets and musicians. He became an outstanding polymath, with publications on secret codes (including writing on the inside of eggshells), physiology, botany, agriculture, engineering, and much else. He wrote more than 20 plays.

Della Porta was particularly interested in the science of light. He made definitive improvements to the camera obscura, a device that projects an image of the outside world into a darkened room; he claimed to have invented the telescope before Galileo, and very likely did. His De refractione optices of 1593 contained the first report of a curious optical effect. He arranged two books so that one was visible to one eye only and the other to the other eye. Instead of seeing a combination of the two images, he perceived them alternately. He discovered that he could select either image at will by consciously switching his attention. This phenomenon is known today as binocular rivalry.

Two other distinct but related effects are impossible figures and visual illusions. In rivalry, each image appears unambiguous, but the eyes are shown conflicting images. In the other two phenomena, both eyes see the same image, but in one case it doesn’t make sense, and in the other it makes sense but is ambiguous.

Impossible figures at first sight seem to be entirely normal, but depict things that cannot exist – such as Roger Shepard’s 1990 drawing of an elephant in which everything above the knees makes sense, and everything below the knees makes sense, but the two regions do not fit together correctly. The Dutch artist Maurits Escher made frequent use of this kind of visual quirk.

In 1832, the Swiss crystallographer Louis Necker invented his “Necker cube” illusion, a skeletal cube that seems to switch its orientation repeatedly. An 1892 issue of the humorous German magazine Fliegende Blätter contains a picture with the caption “Which animals are most like each other?” and the answer “Rabbit and duck”. In a 1915 issue of the American magazine Puck, the cartoonist Ely William Hill published “My wife and my mother-in-law”, based on an 1888 German postcard. The image can be seen either as a young lady looking back over her shoulder, or as an elderly woman facing forwards. Several of Salvador Dalí’s paintings include illusions; especially Slave Market With the Apparition of the Invisible Bust of Voltaire, where a number of figures and everyday objects, carefully arranged, combine to give the impression of the French writer’s face.

Illusions offer insights into how the visual system processes images. The first few stages are fairly well understood. The top layer in the visual cortex detects edges of objects and the direction in which they are pointing. This information is passed to lower layers, which detect places where the direction suddenly changes, such as corners. Eventually some region in the cortex detects that you are looking at a human face and that it belongs to Aunt Matilda. Other parts of the brain are alerted, and you belatedly remember that tomorrow is her birthday and hurry off to buy a present.

These things don’t happen by magic. They have a very definite rationale, and that’s where the mathematics comes in. The top layer of the visual cortex contains innumerable tiny stacks of nerve cells. Each stack is like a pile of pancakes, and each pancake is a network of neurons that is sensitive to edges that point in one specific direction: one o’clock, two o’clock and so on.

For simplicity, call this network a cell; it does no harm to think of it as a single neuron. Roughly speaking, the cell at the top of the stack senses edges at the one o’clock position, the next one down corresponds to the two o’clock angle, and so on. If one cell receives a suitable input signal, it “fires”, telling all the other cells in its stack: “I’ve seen a boundary in the five o’clock direction.” However, another cell in the same stack might disagree, claiming the direction is at seven o’clock. How to resolve this conflict?

Neurons are linked by two kinds of connection, excitatory and inhibitory. If a neuron activates an excitatory connection, those at the other end of it are more likely to fire themselves. An inhibitory connection makes them less likely to fire. The cortex uses inhibitory connections to reach a definite decision. When a cell fires, it sends inhibitory signals to all of the other cells in its stack. These signals compete for attention. If the five o’clock signal is stronger than the seven o’clock one, for instance, the seven o’clock one gets shut down. The cells in effect “vote” on which direction they are detecting and the winner takes all.

Many neuroscientists think that something very similar is going on in visual illusions and rivalry. Think of the duck and rabbit with two possible interpretations. Hugh R Wilson, a neuroscientist at the Centre for Vision Research at York University, Toronto, proposed the simplest model, one stack with just two cells. Rodica Curtu, a mathematician at the University of Iowa, John Rinzel, a biomathematician then at the National Institutes of Health, and several other scientists have analysed this model in more detail. The basic idea is that one cell fires if the picture looks like a duck, the other if it resembles a rabbit. Because of the inhibitory connections, the winner should take all. Except that, in this illusion, it doesn’t quite work, because the two choices are equally plausible. That’s what makes it an illusion. So both cells want to fire. But they can’t, because of those inhibitory connections. Yet neither can they both remain quiescent, because the incoming signals encourage them to fire.

One possibility is that random signals coming from elsewhere in the brain might introduce a bias of perception, so that one cell still wins. However, the mathematical model predicts that, even without such bias, the signals in both cells should oscillate from active to inactive and back again, each becoming active when the other is not. It’s as if the network is dithering: the two cells take turns to fire and the network perceives the image as a duck, then as a rabbit, and keeps switching from one to the other. Which is what happens in reality.

Generalising from this observation, Wilson proposed a similar type of network that can model decision-making in the brain – which political party to support, for instance. But now the network consists of several stacks. Maybe one stack represents immigration policy, another unemployment, a third financial regulation, and so on. Each stack consists of cells that “recognise” a distinct policy feature. So the financial regulation stack has cells that recognise state regulation by law, self-regulation by the industry, or free-market economics.

The overall political stance of any given political party is a choice of one cell from each stack – one policy decision on each issue. Each prospective voter has his or her preferences, and these might not match those of any particular party. If these choices are used as inputs to the network, it will identify the party that most closely fits what the voter prefers. That decision can then be passed to other areas of the brain. Some voters may find themselves in a state akin to a visual illusion, vacillating between Labour and Liberal Democrat, or Conservative and Ukip.

This idea is speculative and it is not intended to be a literal description of how we decide whom to vote for. It is a schematic outline of something more complex, involving many regions of the brain. However, it provides a simple and flexible model for decision-making by a neural network, and in particular it shows that simple networks can do the job quite well. Martin Golubitsky of the Mathematical Biosciences Institute at Ohio State University and Casey O Diekman of the University of Michigan wondered whether Wilson’s networks could be used to model more complex examples of rivalry and illusions. Crucially, the resulting models allow specific predictions about experiments that have not yet been performed, making the whole idea scientifically testable.

The first success of this approach helped to explain an experiment that had already been carried out, with puzzling results. When the brain reassembles the separate bits of an image, it is said to “bind” these pieces. Rivalry provides evidence that binding occurs, by making it go wrong. In a rivalry experiment carried out in 2006 by S W Hong and S K Shevell, the subject’s left eye is shown a horizontal grid of grey and pink lines while the right eye sees a vertical grid of grey and green lines. Many subjects perceive an alternation between the images, just as della Porta did with his books. But some see two different images alternating: pink and green vertical lines, and pink and green horizontal lines – images shown to neither eye. This effect is called colour misbinding; it tells us that the reassembly process has matched colour to grid direction incorrectly. It is as if della Porta had ended up seeing another book altogether.

Golubitsky and Diekman studied the simplest Wilson network corresponding to this experiment. It has two stacks: one for colour, one for grid direction. Each stack has two cells. In the “colour” stack one cell detects pink and the other green; in the “orientation” stack one cell detects vertical and the other horizontal. As usual, there are inhibitory connections within each stack to ensure a winner-takes-all decision.

Following Wilson’s general scheme, they also added excitatory connections between cells in distinct stacks, representing the combinations of colour and direction that occur in the two “learned” images – those actually presented to the two eyes. Then they used recent mathematical techniques to list the patterns that arise in such a network. They found two types of oscillatory pattern. One corresponds to alternation between the two learned images. The other corresponds precisely to alternation between the two images seen in colour misbinding.

Colour misbinding is therefore a natural feature of the dynamics of Wilson networks. Although the network is “set up” to detect the two learned images, its structure produces an unexpected side effect: two images that were not learned. The rivalry experiment reveals hints of the brain’s hidden wiring. The same techniques apply to many other experiments, including some that have not yet been performed. They lead to very specific predictions, including more circumstances in which subjects will observe patterns that were not presented to either eye.

Similar models also apply to illusions. However, the excitatory connections cannot be determined by the images shown to the two eyes, because both eyes see the same image. One suggestion is that the connections may be determined by what your visual system already “knows” about real objects.

Take the celebrated moving illusion called “the spinning dancer”. Some observers see the solid silhouette of a dancer spinning anticlockwise, others clockwise. Sometimes, the direction of spin seems to switch suddenly.

We know that the top half of a spinning dancer can spin either clockwise or anticlockwise. Ditto for the bottom half. In principle, if the top half spins one way but the bottom half spins the other way, you would see the same silhouette, as if both were moving together. When people are shown “the spinning dancer”, no one sees the halves moving independently. If the top half spins clockwise, so does the bottom half.

Why do our brains do this? We can model that information using a series of stacks that correspond to different parts of the dancer’s body. The brain’s prior knowledge sets up a set of excitatory connections between all cells that sense clockwise motion, and another set of excitatory connections between all “anticlockwise” cells. We can also add inhibitory connections between the “clockwise” and the “anticlockwise” cells. These connections collectively tell the network that all parts of the object being perceived must spin in the same direction at any instant. Our brains don’t allow for a “half and half” interpretation.

When we analyse this network mathematically, it turns out that the cells switch repeatedly between a state in which all clockwise cells are firing but the anticlockwise ones are quiescent, and a state in which all anticlockwise cells are firing but the clockwise ones are quiescent. The upshot is that we perceive the whole figure of the dancer switching directions. Similar networks provide sensible models for many other illusions, including some in which there are three different inputs.

These models provide a common framework for both rivalry and illusion, and they unify many experiments, explain otherwise puzzling results and make new predictions that can be tested. They also tell us that in principle the brain can carry out some apparently complex tasks using simple networks. (What it does in practice is probably different in detail, but could well follow the same general lines.)

This could help make sense of a real brain, as new experiments improve our ability to observe its “wiring diagram”. It might not be as ambitious as trying to model the whole thing on a computer, but modesty can be a virtue. Since simple networks behave in strange and unexpected ways, what incomprehensible quirks might a complicated network have?

Perhaps Dalí, and Escher, and the spinning dancer can help us find out. 

Ian Stewart is Emeritus Professor of Mathematics and Digital Media Fellow at the University of Warwick

MARTIN O’NEILL
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The new young fogeys

Today’s teens and twentysomethings seem reluctant to get drunk, smoke cigarettes or have sex. Is abstinence the new form of youth rebellion?

In a University College London lecture theatre, all eyes are on an elaborate Dutch apple cake. Those at the back have stood up to get a better look. This, a chorus of oohs and aahs informs me, is a baked good at its most thrilling.

In case you were wondering, UCL hasn’t rented out a room to the Women’s Institute. All thirty or so cake enthusiasts here are undergraduates, aged between 18 and 21. At the third meeting this academic year of UCL’s baking society, the focus has shifted to a Tupperware container full of peanut butter cookies. One by one, the students are delivering a brief spiel about what they have baked and why.

Sarah, a 19-year-old human sciences undergraduate, and Georgina, aged 20, who is studying maths and physics, help run the baking society. They tell me that the group, which was set up in 2012, is more popular than ever. At the most recent freshers’ fair, more than 750 students signed up. To put the number in perspective: that is roughly 15 per cent of the entire first-year population. The society’s events range from Great British Bake Off-inspired challenges to “bring your own cake” gatherings, such as today’s. A “cake crawl”, I am told, is in the pipeline. You know, like a pub crawl . . . but with cake? Georgina says that this is the first year the students’ union has advertised specifically non-drinking events.

From the cupcake boom to the chart-topping eminence of the bow-tie-wearing, banjo-plucking bores Mumford & Sons, the past decade of youth culture has been permeated by wholesomeness. According to the Office for National Statistics (ONS), this movement is more than just aesthetic. Not only are teenage pregnancies at their lowest level since records began in the 1960s, but drug-taking, binge drinking and sexually transmitted infections among young people have also taken significant dives. Drug use among the under-25s has fallen by a quarter over the past ten years and heavy drinking – measured by how much a person drinks in an average week – is down by 15 per cent. Cigarettes are also losing their appeal, with under-25 smokers down by 10 per cent since 2001. Idealistic baby boomers had weed and acid. Disaffected and hedonistic Generation X-ers had Ecstasy and cocaine. Today’s youth (which straddles Generations Y and Z) have cake. So, what shaped this demographic that, fairly or otherwise, could be called “Generation Zzzz”?

“We’re a lot more cynical than other generations,” says Lucy, a 21-year-old pharmacy student who bakes a mean Welsh cake. “We were told that if we went to a good uni and got a good job, we’d be fine. But now we’re all so scared we’re going to be worse off than our parents that we’re thinking, ‘Is that how we should be spending our time?’”

“That” is binge drinking. Fittingly, Lucy’s dad – she tells me – was an anarchist with a Mohawk who, back home in the Welsh valleys, was known to the police. She talks with deserved pride about how he joined the Conservative Party just to make trouble and sip champagne courtesy of his enemies. Lucy, though decidedly Mohawk-free, is just as politically aware as her father. She is concerned that she will soon graduate into a “real world” that is particularly hard on women.

“Women used to be a lot more reliant on men,” she says, “but it’s all on our shoulders now. One wage isn’t enough to support a family any more. Even two wages struggle.”

***

It seems no coincidence that the downturn in drink and drugs has happened at the same time as the worst financial crisis since the Great Depression. Could growing anxiety about the future, combined with a dip in disposable income, be taming the under-25s?

“I don’t know many people who choose drugs and alcohol over work,” says Tristan, a second-year natural scientist. He is one of about three men at the meeting and it is clear that even though baking has transcended age it has yet to transcend gender to the same extent. He is softly spoken and it is hard to hear him above a room full of sugar-addled youths. “I’ve been out once, maybe, in the past month,” he says.

“I actually thought binge drinking was quite a big deal for our generation,” says Tegan, a 19-year-old first-year linguistics undergraduate, “but personally I’m not into that. I’ve only been here three weeks and I can barely keep up with the workload.”

Tegan may consider her drinking habits unusual for someone her age but statistically they aren’t. Over a quarter of the under-25s are teetotal. Neither Tegan nor Lucy is dull. They are smart, witty and engaging. They are also enthusiastic and seemingly quite focused on work. It is this “get involved” attitude, perhaps, that distinguishes their generation from others.

In Absolutely Fabulous, one of the most popular British sitcoms of the 1990s, a lot of the humour stems from the relationship between the shallow and fashion-obsessed PR agent Edina Monsoon and her shockingly straitlaced teenage daughter, Saffie. Although Saffie belongs to Generation X, she is its antithesis: she is hard-working, moral, politically engaged, anti-drugs and prudishly anti-sex. By the standards of the 1990s, she is a hilarious anomaly. Had Ab Fab been written in the past couple of years, her character perhaps would have been considered too normal. Even her nerdy round glasses and frumpy knitted sweaters would have been considered pretty fashionable by today’s geek-chic standards.

Back in the UCL lecture theatre, four young women are “geeking out”. Between mouthfuls of cake, they are discussing, with palpable excitement, a Harry Potter-themed summer camp in Italy. “They play Quidditch and everything – there’s even a Sorting Hat,” says the tall, blonde student who is leading the conversation.

“This is for children, right?” I butt in.

“No!” she says. “The minimum age is actually 15.”

A kids’ book about wizards isn’t the only unlikely source of entertainment for this group of undergraduates. The consensus among all the students I speak to is that baking has become so popular with their demographic because of The Great British Bake Off. Who knew that Mary Berry’s chintzy cardigans and Sue Perkins’s endless puns were so appealing to the young?

Are the social and economic strains on young people today driving them towards escapism at its most gentle? Animal onesies, adult ball pools (one opened in west London last year) and that much-derided cereal café in Shoreditch, in the East End, all seem to make up a gigantic soft-play area for a generation immobilised by anxiety.

Emma, a 24-year-old graduate with whom I chatted on email, agrees. “It feels like everyone is more stressed and nervous,” she says. “It seems a particularly telling sign of the times that adult colouring-in books and little, cutesy books on mindfulness are such a massive thing right now. There are rows upon rows of bookshelves dedicated solely to all that . . . stuff.” Emma would know – she works for Waterstones.

From adult colouring books to knitting (UCL also has a knitting society, as do Bristol, Durham, Manchester and many more universities), it is hard to tell whether the tsunami of tweeness that has engulfed middle-class youth culture in the past few years is a symptom or a cause of the shrinking interest in drugs, alcohol, smoking and other “risk-taking” behaviours.

***

Christine Griffin is Professor of Social Psychology at Bath University. For the past ten years, she has been involved in research projects on alcohol consumption among 18-to-25-year-olds. She cites the recession as a possible cause of alcohol’s declining appeal, but notes that it is only part of the story. “There seems to be some sort of polarisation going on,” Griffin says. “Some young people are actually drinking more, while others are drinking less or abstaining.

“There are several different things going on but it’s clear that the culture of 18-to-25-year-olds going out to get really drunk hasn’t gone away. That’s still a pervasive social norm, even if more young people are drinking less or abstaining.”

Griffin suggests that while frequent, sustained drinking among young people is in decline, binge drinking is still happening – in short bursts.

“There are still a lot of people going to music festivals, where a huge amount of drinking and drug use goes on in a fairly unregulated way,” she says. It is possible that music festivals and holidays abroad (of the kind depicted in Channel 4 programmes such as What Happens in Kavos, in which British teenagers leave Greek islands drenched in booze and other bodily fluids) are seen as opportunities to make a complete escape from everyday life. An entire year’s worth of drinking, drug-taking and sex can be condensed into a week, or even a weekend, before young people return to a life centred around hard work.

Richard De Visser, a reader in psychology at Sussex University, also lists the economy as a possible cause for the supposed tameness of the under-25s. Like Griffin, however, he believes that the development is too complex to be pinned purely on a lack of disposable income. Both Griffin and De Visser mention that, as Britain has become more ethnically diverse, people who do not drink for religious or cultural reasons – Muslims, for instance – have become more visible. This visibility, De Visser suggests, is breaking down taboos and allowing non-mainstream behaviours, such as not drinking, to become more socially accepted.

“There’s just more variety,” he says. “My eldest son, who’s about to turn 14, has conversations – about sexuality, for example – that I never would’ve had at his age. I think there’s more awareness of alcohol-related problems and addiction, too.”

De Visser also mentions the importance of self-image and reputation to many of the young non-drinkers to whom he has spoken. These factors, he argues, are likely to be more important to people than the long-term effects of heavy drinking. “One girl I interviewed said she wouldn’t want to meet the drunk version of herself.”

Jess, a self-described “granny”, is similarly wary of alcohol. The 20-year-old Liverpudlian, who works in marketing, makes a bold claim for someone her age. “I’ve never really been drunk,” she says. “I’ve just never really been bothered with alcohol or drugs.” Ironically, someone of her generation, according to ONS statistics, is far more likely to be teetotal than a real granny at any point in her life. Jess says she enjoys socialising but her nights out with close friends are rather tame – more likely to involve dinner and one quick drink than several tequila shots and a traffic cone.

It is possible, she suggests, that her lack of interest in binge drinking, or even getting a little tipsy, has something to do with her work ethic. “There’s a lot more competition now,” she says. “I don’t have a degree and I’m conscious of the need to be on top of my game to compete with people who do. There’s a shortage of jobs even for people who do have degrees.”

Furthermore, Jess says that many of her interactions with friends involve social media. One theory put forward to explain Generation Zzzz is that pubs are losing business to Facebook and Twitter as more and more socialising happens online. Why tell someone in person that you “like” their baby, or cat, or new job (probably over an expensive pint), when you can do so from your sofa, at the click of a button?

Hannah, aged 22, isn’t so sure. She recently started her own social media and communications business and believes that money, or the lack of it, is why her peers are staying in. “Going out is so expensive,” she says, “especially at university. You can’t spend out on alcohol, then expect to pay rent and fees.” Like Jess (and as you would probably expect of a 22-year-old who runs a business), Hannah has a strong work ethic. She also has no particular interest in getting wasted. “I’ve always wanted my own business, so for me everything else was just a distraction,” she says. “Our generation is aware it’s going to be a bit harder for us, and if you want to support yourself you have to work for it.” She also suggests that, these days, people around her age have more entrepreneurial role models.

I wonder if Hannah, as a young businesswoman, has been inspired by the nascent strand of free-market, “lean in” feminism. Although the women’s movement used to align itself more with socialism (and still does, from time to time), it is possible that a 21st-century wave of disciples of Sheryl Sandberg, Facebook’s chief operating officer, is forswearing booze, drugs and any remote risk of getting pregnant, in order to get ahead in business.

But more about sex. Do the apparently lower rates of sexually transmitted infections and teenage pregnancies suggest that young people are having less of it? In the age of Tinder, when hooking up with a stranger can be as easy as ordering a pizza, this seems unlikely. Joe Head is a youth worker who has been advising 12-to-21-year-olds in the Leighton Buzzard area of Bedfordshire on sexual health (among other things) for 15 years. Within this period, Head says, the government has put substantial resources into tackling drug use and teen pregnancy. Much of this is the result of the Blair government’s Every Child Matters (ECM) initiative of 2003, which was directed at improving the health and well-being of children and young adults.

“ECM gave social services a clearer framework to access funds for specific work around sexual health and safety,” he says. “It also became a lot easier to access immediate information on drugs, alcohol and sexual health via the internet.”

***

Head also mentions government-funded education services such as Frank – the cleverly branded “down with the kids” anti-drugs programme responsible for those “Talk to Frank” television adverts. (Remember the one showing bags of cocaine being removed from a dead dog and voiced by David Mitchell?)

But Head believes that the ways in which some statistics are gathered may account for the apparent drop in STIs. He refers to a particular campaign from about five years ago in which young people were asked to take a test for chlamydia, whether they were sexually active or not. “A lot of young people I worked with said they did multiple chlamydia tests throughout the month,” he says. The implication is that various agencies were competing for the best results in order to prove that their education programmes had been effective.

However, regardless of whether govern­ment agencies have been gaming the STI statistics, sex education has improved significantly over the past decade. Luke, a 22-year-old hospital worker (and self-described “boring bastard”), says that sex education at school played a “massive part” in his safety-conscious attitude. “My mother was always very open [about sex], as was my father,” he says. “I remember talking to my dad at 16 about my first serious girlfriend – I had already had sex with her by this point – and him giving me the advice, ‘Don’t get her pregnant. Just stick to fingering.’” I suspect that not all parents of millennials are as frank as Luke’s, but teenagers having sex is no longer taboo.

Luke’s attitude towards drugs encapsulates the Generation Zzzz ethos beautifully: although he has taken MDMA, he “researched” it beforehand. It is this lack of spontaneity that has shaped a generation of young fogeys. This cohort of grannies and boring bastards, of perpetual renters and jobseekers in an economy wrecked by less cautious generations, is one that has been tamed by anxiety and fear.

Eleanor Margolis is a freelance journalist, whose "Lez Miserable" column appears weekly on the New Statesman website.

This article first appeared in the 05 February 2015 issue of the New Statesman, Putin's war