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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

© MARK PETERSON/REDUX/EYEVINE
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Goodbye to the Confederate flag

After the shootings in Charleston, the Republican right showed it was finally ready to reject the old symbols of the Confederacy.

On 27 June, an African-American activist named Bree Newsome woke up before dawn, put on her climbing equipment and scaled a 30-foot flagpole on the lawn of State House in Columbia, South Carolina. She then removed the Confederate battle flag that flew from it. “We can’t wait any longer,” she explained later in an online statement. “It’s time for a new chapter where we are sincere about dismantling white supremacy.”

After she was led away in handcuffs, the flag was raised again.

Newsome’s protest reflected a growing impatience within America’s black community and anger about liberal inaction. Political rallies by the Democratic presidential contenders Hillary Clinton and Bernie Sanders have been disrupted by the Black Lives Matter campaign against violence committed on young African Americans and the cultural and legal biases that justify it. While promoting his book on race in the US, the writer Ta-Nehisi Coates argued that, to African Americans, the battle flag represents a lingering attempt “to bury the fact that half this country thought it was a good idea to raise an empire rooted in slavery”.

Yet, on this matter, to everyone’s surprise, the black civil rights movement and many southern Republicans have proved to be of one mind. On 9 July the House of Representatives in South Carolina voted to lower the battle flag for good. It stood, representatives said, for racism. It had to go.

The context of this agreement was a painful one. Ten days before Newsome’s act, a 21-year-old white man named Dylann Roof shot and killed nine black worshippers at the Emanuel African Methodist Episcopal Church in Charleston, South Carolina. According to his room-mate, he wanted to start a race war. The TV screens showed a photo of him holding a gun in one hand and a Confederate battle flag in the other.

If the demands for redress made by civil rights groups didn’t come as a surprise, conservative acquiescence did. The Republican Party had built a solid base in the South by courting white voters who cherished the memory of the Confederacy. Yet the party’s presidential hopefuls from both the North and the South – including Jeb Bush, Lindsey Graham, Scott Walker and George Pataki – said that the battle flag ought to be lowered. The most striking intervention was made by the governor of South Carolina, Nikki Haley, who denounced the use of the Confederate flag and signed the bill removing it. Haley is now tipped to figure on the list of potential vice-presidential nominees.

The volte-face of the US right is in part a result of the horror of the Charleston shootings. Yet it also occurs in the context of major shifts within American society. There are still many conservatives who will defend Confederate heritage as a matter of southern pride but the culture wars are changing as the US becomes increasingly European in outlook. This is taking place across the country. It just happens to be more pronounced in the South because no other region has fought so violently and so long to resist the liberal tide.

The story of the battle flag is the story of the South. The first official Confederate flag used in the civil war of 1861-65 caused confusion during fighting – through the haze of gun smoke, its design of 13 stars and red and white bars was hard to distinguish from the Stars and Stripes. An alternative blue cross was rejected for being too sectarian; the racist Confederacy was anxious not to offend its Jewish citizens. So the cross became a diagonal X. This flag was never officially adopted by the Confederate army. In the years after the war its use was infrequent.

There was little need to visualise southern difference in a flag. It was self-evident in the physical signs of racial segregation: separate schools, pools and drinking fountains; black people confined to the back of the bus. Political displays of the battle flag of Dixie (the historical nickname for the states that seceded from the Union) only really resurfaced when that racial order was challenged by northern liberals. In 1948, the Democrats – then the party overwhelmingly in control of the South – split over modest calls for civil rights. The conservatives who refused to support that year’s presidential ticket, the “Dixiecrats”, triggered a rev­ival of flag-waving across the region.

The old battle flag suddenly appeared on private lawns, on cars and at political rallies. Supposedly ancient cultural traditions were invented overnight. For instance, the 1948 student handbook of the University of Mississippi confessed: “Many Ole Miss customs are fairly new; they lack only the savouring which time brings . . . Ole Miss has adopted the Confederate flag as a symbol of the Mississippi spirit. Each football game finds the scarlet flag frantically waving to the rhythm of the Rebel band.”

I can confirm that this “tradition” was still going as recently as in 2005. That year, I attended an American football game at Ole Miss and was surprised when the band played “Dixie” at the end. White boys and white girls stood up and belted out the folk song of the Confederacy, while black students filed out.

In 1958, South Carolina made it a crime to desecrate the battle flag. Three years later, on the 100th anniversary of the outbreak of the civil war, it was hoisted above its Capitol building in Columbia. That day, there was a struggle in the US Congress to keep federal funding going for segregated schools.

So clear is the link between the postwar white resistance to civil rights and the battle flag that many see it as the symbolic equivalent of the N-word. Jack Hunter, the editor of the conservative website Rare Politics, says: “Some people insist that it’s not about racism, not about slavery, not about segregation. But it’s about all those things.” Hunter grew up in Charleston and used to skateboard in the car park of the church that Dylann Roof attacked. When he was a young journalist, he appeared on local radio as a rabidly right-wing masked character called “the Southern Avenger”. His past was exposed in 2013 while he was working for Rand Paul, a Republican presidential candidate, and Hunter stepped down from his position. He publicly renounced his youthful association with racial conservatism. He now eschews any romanticism about the Confederate cause and its demand for states’ rights. “States’ rights to do what?” he asks: the right to discriminate against African Americans? He is glad that the State House flag is gone. He ascribes its longevity to ignorance, which was corrected by Roof’s rampage: “It was the first time that [southern Republicans] were able to see a different perspective on this symbol.”

Not everyone agrees. Richard Hines – a former South Carolina legislator, Reagan campaign state co-chair and senior activist with the Sons of Confederate Veterans – insists that the flag is “an enduring symbol of the southern fighting man”. Indeed, a poll in July found that 57 per cent of Americans think it stands for southern heritage, rather than racism. Yet that heritage has a political dimension. “Southern people are proud of who they are and there is a leftist assault to destroy the best part of America,” Hines says. “The Trotskyite elite in control of the establishment wants to root out the southern tradition” – a tradition of religious devotion, chivalry and military honour. It is possible to cast the battle flag as a pawn in a much larger cultural conflict.

In 2000, civil rights activists lobbied hard to get the battle flag removed from the top of the South Carolina Capitol and succeeded in having it shrunk in size and relocated to the grounds of State House. The issue came up in that year’s Republican presidential primaries – an unusually poisonous contest between George W Bush and John McCain. Supporters of Bush put out a false story that McCain had fathered an interracial child out of wedlock. McCain added to his woes by opining that the battle flag was “a symbol of racism and slavery”. An organisation called Keep It Flying flooded the state with 250,000 letters attacking him and he lost the crucial competition here to Bush.

The battle flag has retained a strong emotional power for a long time. This makes the Republican establishment’s abandonment of the flag all the more surprising. Then again, those who run the South are probably the people most likely to grasp how much the region has changed in just a decade.

***

In 2010 I took a trip through North Carolina. The landscape told a story. Dotted along the roadside were abandoned black buildings, the old tobacco sheds. The decline of the rural economy had rendered them obsolete. Over the fields that would once have been full of farmers were freshly tarmacked roads, stretching out to nowhere. My guide explained that these were supposed to be cul-de-sacs for new houses. North Carolina was going through a property boom. But who was going to buy all those homes, I asked? The answer: damn Yankees.

Demography is destiny. This once agri­cultural region developed fast from the 1960s onwards by keeping union membership, taxes and regulation as low as possible. Yet capitalism proved disastrous for southern conservatism. Northerners flooded in, seeking work or retirement and bringing their own values. The forecast is that North Carolina’s Research Triangle – the South’s Silicon Valley – will grow by 700,000 jobs and 1.2 million people in two decades.

White migration was accompanied by an influx of Spanish speakers as the service sector flourished. Between 2000 and 2010, the white share of the population of North Carolina fell from 70 to 65 per cent. The black proportion remained at roughly 21 per cent. The Latino proportion, however, jumped from 4.7 per cent to 8.4 per cent. Today, the proportion of people who are non-white and over 60 is about a third. But it’s approaching nearly half for those under 18. As a result, politics in the South is no longer biracial: a contest between white and black. It is increasingly multiracial and uncoupled from the region’s complex past.

The impact of these changes is reflected in voting patterns. In 2000, the South was still overwhelmingly Republican in presidential contests. Even the Democratic nominee, Al Gore, a southerner, lost his home state of Tennessee. But in 2008 and 2012, Barack Obama took those states with the fastest-changing demographics: Florida and Virginia. He won North Carolina in 2008 and lost it in 2012 – but by less than 100,000 votes. It is true that the Republicans won back control in the 2014 midterm elections, with the result that the Deep South now sends few Democrats to Congress; but the region’s political masters are not quite as traditional-minded as they once were.

The Republican relationship with the Confederate past is complex. As the party of Abraham Lincoln and the Union, the GOPs’ southern support was historically small. But in the 1960s the national Democratic Party embraced civil rights and alienated its once loyal southern following; the Republicans took the opportunity to steal some conservative white voters.

The growing southern Republican vote had a class component. Its success in local and congressional races was built more on winning over middle-class moderates than on appealing to the working-class racists who filled the ranks of the Ku Klux Klan. The southern Republican Party did enthusiastically embrace the Confederate battle flag in many quarters. But some office-holders did so only with ambiguity, while large sections of the party never identified with it at all. The period of Republican ascendancy in the South was, in reality, linked with a softening of the area’s racial politics.

Two of the Republicans’ current southern stars are Indian Americans: Bobby Jindal, the governor of Louisiana, and Nikki Haley, the anti-flag governor of South Carolina. There are just two black people in the US Senate and one of them is a Republican, the Tea Party-backed senator for South Carolina, Tim Scott. Marco Rubio, the Floridian senator and presidential candidate, is Cuban American, and the former Florida governor Jeb Bush is married to a Mexican-born woman and speaks fluent Spanish. Bush has tried to push a more moderate line on immigration, in deference to how the GOP will struggle to win the White House if it appeals only to angry white voters. The Kentucky libertarian senator Rand Paul, Jack Hunter’s former boss, has called for legal reforms to correct the trend of keeping far more black than white people in prison. And he is not the only Republican to have been moved by recent race riots sparked by police violence.

***

Violence on the streets of Ferguson, Missouri, and Baltimore, Maryland, confirmed that there still is a culture war in the US. Yet its character has changed. In the past, civil disturbances were typically leapt upon by conservative politicians as evidence of social decline. The 1992 LA riots were blamed on single parenthood and rap lyrics. In contrast, conservative leaders today are far more likely to acknowledge the problems of white racism. There is no place in their ranks for the likes of Dylann Roof. White supremacists are tiny in number.

Jack Hunter claims: “The KKK is like 12 guys in a telephone booth. Liberal groups will use their threat for fundraising but it doesn’t exist. It hasn’t properly since the 1960s.” Roof’s actions say more about gun control, mental illness and the angst of the young than they do about popular, largely liberal views on race, as polling shows.

We can see a similar liberal shift in other areas of the historic culture war. In May 2015 Gallup released the results of a “moral acceptability” survey charting changes in national attitude across all age groups, from 2001 to 2015. Approval of gay relationships jumped from 40 to 63 per cent; having a baby out of wedlock from 45 to 61 per cent; sex between unmarried men and women from 53 to 68 per cent; doctor-assisted suicide from 49 to 56 per cent; even polygamy went from 7 to 16 per cent. Abortion remained narrowly disapproved of: support for access has only crept up from 42 to 45 per cent. This is probably a result of an unusual concentration of political and religious opposition and because it involves a potential life-or-death decision. But the general trend is that young people just don’t care as much about what consenting adults get up to.

Why? It might be because old forms of identity are dying. One way of measuring that is religious affiliation. From 2007 to 2014, according to Pew Research, the proportion of Americans describing themselves as Christian fell from 78 to 71 per cent. Today, only a quarter of the population is evangelical and 21 per cent Catholic, down despite high immigration. Then there is the decline in civic or communal activity. Since 2012, the organisers of Nascar, the stock-car races, have not published attendance figures at their tracks, probably because they have fallen so sharply. The decline of this most macho and working class of sports parallels the fall in conservative forms of collective identity such as southern traditionalism.

The old culture war was, like the racial politics of the old South, binary. In the 1950s, around the same time as the South invented its tradition of flying the battle flag in colleges, the US constructed an ideal of the “normal” nuclear family unit: straight, white, patriarchal, religious. On the other side was the “abnormal”: gay, black, feminist, atheist, and the rest. The surest way to get elected in the US between 1952 and 2004 was to associate yourself with the economic needs and cultural prejudices of the majority. The approach was once summed up by a Richard Nixon strategist thus: split the country in two and the Republicans will take the larger half. But that is changing. The old normal is no longer the cultural standard but just one of many identities to choose from. The races are mixing. Women want to work more and have children later in life, possibly without marriage. Many religious people are having to rethink their theology when a child comes out as gay. And the enforcers of the old ways – the unions, churches or political parties – are far less attractive than the atomising internet.

***

Politicians are scrabbling to keep up with the diffusion of American identity. Democrats got lucky when they nominated Barack Obama and chose a presidential candidate who reflected the fractured era well: interracial, non-denominational Christian, and so on. In the 2012 presidential race the Republicans got burned when they tried to play the old culture war card on abortion. They won’t repeat that mistake. After the Supreme Court legalised gay marriage across the country in June, the right’s response was not as uniformly loud and outraged as it would have been in the past. Some protested, but serious presidential contenders such as Jeb Bush grasped the implications of the defeat. There is a cultural and political realignment going on and no one is sure where it will lead. It’s encouraging caution among the Republican top brass. It is time, they think, to abandon lost causes.

The death of southern traditionalism is part of the ebb and flow of cultural history. Identities flourish and die. As political fashions change, you find the typically American mix of triumph on one side and jeremiad on the other. Richard Hines stood vigil as the battle flag was lowered in Columbia and noted with disgust the presence of what he described as “bussed-in” activists. “They pulled out all these gay pride flags and started shouting, ‘USA, USA, USA!’ It reminded me of the Bolshevik Revolution.”

Hines reckons that more southerners will now fly the flag than ever before and says he has attended overflow rallies of ordinary folks who love their region. He may well be correct. The faithful will keep the old Confederate standard fluttering on their lawns – an act of secession from the 21st century. But in the public domain, the battle flag is on its way down and in its place will be raised the standard of the new America. The rainbow flag flutters high. For now.

Tim Stanley is a historian and a columnist for the Telegraph

This article first appeared in the 20 August 2015 issue of the New Statesman, Corbyn wars