The dress is white and gold. But here's why we disagree

(Image: Swiked/http://bit.ly/17Cbamm)

It could be simultaneously both the biggest and the smallest controversy to hit the internet since, well, ever. What colour is the dress? A Tumblr user uploaded a picture of a dress, saying that they were having an argument about what colour it is. Is it white and gold or blue and black? Buzzfeed republished it and it broke even their records for traffic.

There are already many explanations, and most are wrong. But fear not, New Scientist can explain it.

(Image: Adrian Pingstone)

You've probably seen optical illusions like this one above.

Believe it or not, the two squares, A and B, are exactly the same shade of grey. Because there are cues in the image telling you to imagine that B is in shadow, you interpret it as a light coloured square, made darker by being in shadow.

But as Erin Goddard from Macquarie University in Sydney, Australia, points out, a similar trick can be done with colours too. Look at this version below:

(Image: Dale Purves)

Both squares are grey, but you see one as yellow and one as blue. It happens because in both cases you unconsciously correct for what colour you think the source of light is.

We do that all the time to get by in the world: the reason you see a piece of white paper as white regardless of whether you're outside (under the blue sky) or inside (under red-tinted candle light) is because you shift the colour of the paper in your mind back to white – you white balance it. Or in technical terms, you "discount" for the "colour of the illuminant".

In the illusion above, on the left you correct for a light source you think is yellow, making the grey square appear blue. And on the right you do the opposite.

So now to that dress. The key thing is that we are correcting for an imagined light source, just as in the example above. But there are two features of this picture that make it very difficult to interpret, which means people are likely to see it differently.

Firstly, the dress is actually a complicated mixture. If you find the RGB values of the gold/black, they come out as a "yellowish/gold/brown" says Bart Anderson from the University of Sydney. Meanwhile, the "white/blue" is a mixture too. "If you look at the image itself – the colours in the image – they are gold and very light blue," he says, clearly taking a side in the controversial dispute.

The second feature that makes it ambiguous is that there are not many cues in the picture to tell you how to interpret the colour of the light source. You can't even tell if it's in shadow or not, which could make all the difference, says Goddard.

"In addition to making things darker, shadows often 'change' the colour of part of a scene – eg if there's a sunny scene, the direct sunlight is quite yellow, but areas in shadow are mostly lit by skylight, which is quite blue," she says. "Artists know about it – they know to add blue to shadows to make them more convincing."

Without cues telling you how to correct for the light source, people can be left fumbling and possibly just randomly fall into one category. And once you see it that way, it's hard to change.

"It's actually consistent with a few different interpretations but rather than seeing it as 'oh, it could be this or it could be that' you tend to just make a guess and stick with that until you've got evidence to the contrary," says Goddard.

It can then be very surprising to hear that it's not the same for everyone. Goddard says a similar thing happens with the well-known spinning ballerina. You can see it either way, but it once you see it one way or the other, it's very hard to switch.

Anderson says that feature of this illusion struck him. He started off as a white/golder. In fact, when New Scientist first contacted him he thought it was a hoax. "Do either of you see anything remotely black about this dress?" he asked me and another researcher over email. But after playing with the image for a while switched to a black/bluer. "I can't get my original percept back. Usually when this happens, I can see both. So it's very interesting."

But it could also be something to do with people's internal biases, says Anderson. "People may have different estimates of the colour balance – ie, what counts as 'neutral'," he says. Since this illusion so strongly splits people into different camps, it could be interesting to learn about the nature of those inherent biases. "Although it's not clear how it will tell you much more than that yet," he says.

Amazon is selling what appears to be the same dress. In this photo it looks blue and black.

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Treating inherited disease could start in the womb

For a baby born with genetic disease, a lifetime of treatment can ensue. But research in mice suggests that treatment for haemophilia – and maybe other inherited diseases – could start in the womb, boosting the success of therapies after birth.

Our immune systems are pretty good at identifying and destroying foreign material. Once we've encountered a particular invader, our immune cells mount a quicker response should it ever turn up again. This is the rationale behind vaccinations.

But this mechanism can cause problems when we want the body to accept foreign material in, say, the form of a donated organ. But this isn't always the case. In the 1950s, a group of researchers at University College London discovered that exposing the immune system to foreign material in the womb can have the opposite effect.

The team was grafting skin from one strain of mice to another. The new skin tended to get destroyed by the recipient animals' immune systems. But when the group injected cells from the donor mice into developing fetuses, the mice that were born were much more likely to accept the skin graft. It seemed they had been primed to the foreign cells while in the womb, and developed a tolerance.

Damaging defence

Sébastien Lacroix-Desmazes at INSERM, the French national institute of medical research in Paris, and his colleagues wondered whether triggering this priming effect might help treat inherited conditions, such as haemophilia.

In haemophilia, genetic mutations cause a lack of blood clotting proteins. The most common type is caused by a lack of coagulation factor VIII. People born with the disorder can be given injections of factor VIII, but the immune systems of about one-fifth of people with haemophilia develop antibodies that render the protein ineffective.

To see if priming in the womb would make any difference to this immune response, Lacroix-Desmazes's team attached parts of factor VIII to another protein that enabled it to cross the placenta between mother and fetus. The group then administered this to pregnant mice lacking factor VIII. Other similar pregnant mice received no treatment.

Once the pups were born, the team treated all of the offspring with a factor VIII therapy. The mice treated while in the womb were much more tolerant of the protein – on average, their immune systems produced 80 per cent less antibody against it than the control mice.

Black box of development

The team hopes that a similar approach could be useful in other disorders caused by a lack of a protein, such as Pompe disease – a rare, potentially fatal inherited disease characterised by muscle weakness and heart defects.

We are still some way off using these therapies in people, says Mike McCune at the University of California, San Francisco. We don't know the ideal dose for a fetus, when it should be used or whether it would have any untoward effects on either the mother or the baby, he says.

"We know precious little about the immune system of the human fetus and the human newborn," says McCune. "The third trimester is a total black box of human fetal development, because we have no way to study it."

Sing Sing Way, an infectious disease physician and scientist at the Cincinnati Children's Hospital Medical Center in Ohio, agrees that it is early days. "The study shows that this approach can work in mice, but does little to say how it may actually work as a therapy or preventative strategy for humans."

However, both say exploring the idea of fetal immune therapy is worthwhile.

"If you found a safe way to do this, you could imagine developing treatments for allergies," says McCune. People can be genetically predisposed to allergies, and allergies developing in childhood are a huge problem, he says.

Other autoimmune disorders, including type 1 diabetes, which has a genetic component, could also represent a target for this approach, says Way, so it is potentially of enormous value.

Journal reference: Science Translational Medicine, DOI: 10.1126/scitranslmed.aaa1957

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Programmable pop-up materials can morph on command

Normally you can rely on solid objects to hold their shape: aeroplane wings are skinny teardrops, paper is flat and chairs are good for sitting on. But the US air force has found a way to change that. They have made flat surfaces pop into complex 3D shapes when heated – an ability that could find uses in fields from medicine to flight.

"Think of an antenna that changes its radiation properties depending on its shape, or morphing wings where the shape dictates the function," says Taylor Ware at the Wright-Patterson Air Force Base in Ohio. Although confined to the lab for now, the technique has the potential to make shape-shifting objects a part of normal life.

To build their morphing device, the team used a thin film of liquid crystal elastomers – a material made of elastic polymers that also contains a crystal lattice. Polarised laser light then changes the way the units that make up the lattice are aligned. Because the crystal's thermal properties are not the same in all directions, heating the new arrangement makes some parts of the lattice expand and others contract.

Ordering the crystals just so makes different parts expand and contract against each other such that heating a flat sheet to 175 degrees Celsius makes it morph into a predetermined 3D shape that can be 100 times as tall as the film is thick. Ware says there may be other ways to trigger the shape change that are less extreme, although also less effective, including the application of organic solvents, and potentially even water.

Shape-shifting medicine

Ware and his colleagues adapted their process from the way companies make LCD televisions, so it could plausibly be scaled out of the lab and into the real world.

"Large area sheets of these polymers would be quite accessible," he says. "We certainly have interest in bringing this toward some sort of device in the long term."

Ware thinks biomedical applications are likely to be the first out of the gate, perhaps creating easily implantable devices that can be triggered to morph once inside the body. Just as programming pushed applications for computers beyond their mathematical roots, so programmable matter might expand what our stuff can do.

Journal reference: Science, DOI: 10.1126/science.aaa6579

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Kitchen-table physics lets you do big science at home

(Image: Spencer Wilson)

Five groundbreaking experiments for a low-tech lab: from a solar storm detector in a jam jar to a Large Hadron Collider in your salad bowl

JAMIE EDWARDS is every bit the nuclear scientist – curious, diligent and passionate about unlocking the energy stored inside atoms. Last year, having scoured the web for parts and blueprints, he built his first working fusion reactor. The project would have been a tremendous feat for anyone, but in Jamie's case there was an additional wow factor: he was just 13.

Jamie found himself propelled to global stardom by his achievement. The media were abuzz with excitement that the same process that makes the sun shine had been harnessed in Penwortham, a small town in northern England. The US television host David Letterman invited Jamie on to his chat show to discuss what prompted him to set about fusing hydrogen ...

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Britons may have imported wheat long before farming it

Prehistoric people living on the British Isles were more than hunter-gatherers: they were bakers, too, a discovery suggests. They seem to have been eating wheat some 2000 years before it was cultivated in the region.

A find of plant DNA challenges the assumption that the grain didn't arrive until agriculture took hold there around 4000 BC. People were in fact enjoying flour imported from mainland Europe some 2000 years before this.

"Rather than being cut off as the commonly held view states, these hunter-gatherers had trade links to distant agricultural communities," says Robin Allaby from the University of Warwick, UK.

Allaby and his team's claim is based on a discovery at an undersea site around 12 kilometres from the Isle of Wight, off the coast of southern England. In the Mesolithic Age – some 10,000 to 5000 years ago, before farming emerged – the area was above the waves and was the site of a shipyard. Using pioneering techniques to analyse the sediment dug from beneath the sea floor, they found plentiful wheat DNA from this era – 2000 years earlier than any other signs of wheat previously found in the UK.

However, the lack of the pollen in the samples suggests that nobody was growing wheat here. And as the closest wheat-farming communities were probably in southern Europe or the Near East, getting a loaf of bread would have required a substantial trek. Occasional examples of trade across Europe from this time do exist, but this is the first evidence that hunter-gatherers were willing to travel long distances for rare foodstuffs.

Fond of flat bread

The fact that no husks or seed casings turned up in the mud suggests that these communities got their wheat in the form of flour. So it is likely that the boat builders had a fondness for flat breads to complement their protein-rich diet of game and foraged nuts and plants, says Allaby.

Dorian Fuller from University College London believes that the rare grain was probably a status symbol rather than an important part of hunter-gatherers' diets. Much like the spice trade that flourished in more recent times, the exotic and distant origins would have made wheat highly desirable for those looking to show off.

Valuable foodstuffs were often the first commodities to be traded over long distances, as later crops – African sorghum arriving in India and wheat in China, for instance – bear out. Fuller sees no reason why it would be any different for Mesolithic communities.

Pete Rowley-Conwy of Durham University, UK, is deeply sceptical of the new finding, which flies in the face of the accepted view of how grain cultivation and consumption spread throughout Europe, though. "It is not impossible," he says, "but the distances involved make the whole idea extremely unlikely."

He is unwilling to throw out a consensus from thousands of previous finds, based on just one study.

Journal reference: Science, DOI: 10.1126/science.1261278

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Future-predicting neurons discovered in the brain

We meet in a pub, we have a few drinks, some dinner and then you lean in for a kiss. You predict, based on our previous interactions, that the kiss will be reciprocated – rather than landing you with a slap in the face.

All our social interactions require us to anticipate another person's undecided intentions and actions. Now, researchers have discovered specific brain cells that allow monkeys to do this. It is likely that the cells do the same job in humans.

Keren Haroush and Ziv Williams at Harvard Medical School trained monkeys to play a version of the prisoner's dilemma, a game used to study cooperation. The monkeys sat next to each other and decided whether or not they wanted to cooperate with their companion, by moving a joystick to pick either option. Moving the joystick towards an orange circle meant cooperate, a blue triangle meant "not this time".

Neither monkey could see the other's face, or receive any clues about their planned action.

If the monkeys cooperated, both received four drops of juice. If one cooperated and the other decided not to, the one who cooperated received one drop, and the other received six drops of juice. If both declined to work together they both received two drops of juice.

The big reveal

Once both had made their selections, they could see what the other monkey had chosen and hear the amount of juice their companion was enjoying.

The monkeys played the game several thousand times. Like humans, they were more likely to cooperate if their opponent had recently cooperated in a previous trial.

During the experiment, the team recorded brain activity from single cells in the monkeys' anterior cingulate – an area thought to play a role in decision-making. They discovered that the activity of a specific set of neurons was associated with the monkey's own decision in each game.

But anticipating your opponent's action, on the basis of previous behaviour, is the key to receiving the greatest reward in the prisoner's dilemma. Haroush and Williams found another set of neurons within the same area that were responsible for predicting what the monkeys' opponent was intending on doing – before they did it.

I can read your mind

In fact, when the team looked back at the results, in 79 per cent of trials, the activity of the neurons in one monkey predicted the subsequent move of the other monkey.

The researchers say that unlike mirror neurons – which are thought to be active when people and other animals observe an action or perform the same action as another – these neurons try to predict the intentions of others.

To confirm their findings, the team repeated the experiment with the same monkeys but had them play against a computer rather than a companion. This time the monkeys were less likely to cooperate or reciprocate a past offer of cooperation from their opponent.

Selfish and alone

When playing in this isolated context, says Williams, the neurons responsible for the monkey's own choice became more active than those that were previously busy trying to predict decisions. "This might explain the monkey's selfish behaviour in this condition," Williams says.

The researchers then went a step further and disrupted the activity of these predictive neurons by inhibiting them with weak electrical pulses, while the monkeys played the game next to each other. Again the monkeys were less likely to cooperate even after their opponent had cooperated previously.

Haroush and Williams suggest that the discovery might aid the development of new treatments for conditions such as autism and antisocial disorders. "It may be that the cingulate is important for reinforcing mutually beneficial social interactions among individuals, and therefore may be a targeted hub for treating disorders in which these abilities are impaired," says Haroush.

Journal reference: Cell, DOI: 10.1016/j.cell.2015.01.045

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The Nether: Real morality for a virtual world

A new play uses the idea of paedophilia in a simulated reality to raise tough questions about how we should behave in virtual spaces

The play relies on suggestion, not shock (Image: Johan Persson)

"Who are we when we live without consequences?" That's the question a detective poses angrily to the owner of the Hideaway, a virtual clubhouse catering to paedophiles in The Nether, Jennifer Haley's charged, compact play about online morality. The "Nether" of the title, a fully immersive relative of today's internet, lets them indulge in fantasies of molestation and murder – without ever meeting an actual child.

To Morris, the detective, the corruption of the Hideaway's clientele is real, even if their victims are not. Yet for all the pent-up fury with which she argues her case, she cannot induce Poppa, the Hideaway's charismatic proprietor, to admit he has done anything wrong.

Indeed, he insists that in his closely regulated realm – an idyllic and stunningly realised colonial manse – customers can expend their urges entirely safely. Everyone consents, no one comes to harm, and they are happy, as they could never be in the real world. What's wrong with that?

Outside the comfort zone

This is not a comfortable scenario, and The Nether is not a comfortable play; it takes courage to write anything that presents paedophiles in terms other than outright condemnation. Yet Haley's script does not require us to condone paedophilia, only to recognise that paedophiles have desires, motives and emotions too.

And it is remarkable how every character retains their complex humanity no matter what virtual atrocities we know they've committed.

It reminds us that if we regard them as sick – a favourite tabloid descriptor – we must think of them as needing cures, too. For those wary of what they might see, by the way, the play's power relies on suggestion, not shock.

The Nether's audience is confronted by unanswered and perhaps unanswerable moral propositions at every turn of its 85 minutes. Is freedom of speech absolute? Should you ever be prosecuted for the contents of your imagination? Does moral corruption lead to physical degradation? If no one is being forced to act against their will, should such actions nonetheless be forbidden?

In the frictionless Nether, stripped of real-world complications, the arguments are pared to their essentials, sometimes leaving the characters and the audience scrabbling for purchase. For example, Morris is desperate to learn whether there was ever "a real girl" beneath the Hideaway's simulacrum of 11-year-old Iris. The implication is that Poppa would then clearly be complicit in abuse, just as those who trade images of abuse today are complicit in their manufacture.

But such assurance is not easy to come by: every time the audience is tempted to think that we are approaching certitude, Haley's script snatches it away. By assuming the technology, and abstracting the problem, she allows the audience to focus on the Socratic method at the play's core and weigh up the protagonists' arguments in a relatively cool-headed manner.

Freedom's limits

And while Haley has picked the most extreme case around which to build her play, the way it probes the limits of freedom, morality and society has much broader relevance. You need look no further than the image-based forum 4chan, or perhaps even Twitter, to appreciate that.

But on the other hand, this approach also means it's hard to relate The Nether to the realities of our world.

We know that some paedophiles have a compulsive urge to abuse because of a brain injury, for example. Others have formed support groups to help them resist their urges, reportedly with some success. So it is hard to imagine that what works for one will work for all.

And our virtual reality technologies have not yet reached the point where online activities can convincingly substitute for real ones, which means that living without consequences remains the stuff of science fiction.

Almost science fact

But The Nether is only just science fiction. Debate began some years ago about the legality and morality of simulated child pornography: does it slake or fuel paedophilic lust? Virtual children have been used to ensnare paedophiles, although there have also been suggestions that childlike sex robots could be used to treat them.

Given recent rapid advances in haptics and virtual reality, combined with ready extrapolation from today's "dark net", the world depicted in the play where some sites don't appear in any search index and are sealed off from outside scrutiny may not be that far off.

If that future does arrive, how will we deal with it? The Nether is a stark reminder that, lacking the evidence and perhaps the will, we have ducked many of the toughest questions about how to behave in virtual spaces. The Nether, dark though it is, makes a compelling case that we should now engage fully: its critique of our times is breathtakingly powerful. Let's hope it doesn't prove equally powerfully prescient about times to come, too.

The Nether by Jennifer Haley, Duke of York's Theatre, London, until 25 April

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Memory lapse draws bumblebees to untried flowers

Bumblebees can recall which flowers yield nectar, but like people they can get mixed up – leading them to home in on flowers they have no experience of

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Memory lapse draws bumblebees to untried flowers

Ever remembered something wrongly? Sworn blind that something had happened, when in fact it hadn't? Bumblebees also appear to have the same problem.

In their everyday lives, bumblebees have a lot to remember: the colours, patterns, scents and symmetries of flowers, the best ways to get food from the best ones, as well as their locations and how to get to them. Relative to their lifespan, bumblebees have a good long-term memory for these details. They learn very early how to manipulate flowers to get nectar or pollen out of them, and still remember this three weeks later, towards the end of their short lives.

But they do make mistakes. "Bees can memorise more than one flower type, though there are costs," says Lars Chittka of Queen Mary University of London. "Bees make more mistakes when they juggle multiple memories than if they just focus on one flower type."

Chittka and his colleague Kathryn Hunt decided to investigate whether bees can have false memories, as humans often do. These are instances in which an individual remembers something that they have never actually experienced or been exposed to, a problem not only for witnesses in criminal trials but also for students, who may misremember what they were taught.

Memory merge

To see if bees misremember in a similar way, the researchers trained bees using artificial flowers that were either yellow or had a black-and-white ringed pattern. Both types of flower offered a nectar-like reward, but at different times. When tested within minutes of their training, bees usually visited a flower of the type that had most recently rewarded them.

A day or so later, Chittka and Hunt tested the bees' long-term memories. As time wore on, bees that had first been rewarded by ringed flowers, and later by yellow flowers, started to do something strange. By the end of the experiment, they were often opting for a completely new type of flower – one with yellow and white rings.

The bees had never learned that such a pattern would offer a reward, but seemed to have become confused, choosing to visit a flower that shared features with both types of flower it had previously encountered. They appeared to have merged their memories to create a false one.

"There might be items in a bumblebee's memory library that they have never actually encountered in real life," says Chittka.

"This research shows that memory errors, similar to some to which we are also victim, occur in a very distantly related species, an insect, and therefore suggests that all nervous systems share some common memory mechanisms," says Stefano Ghirlanda at the City University of New York.

"Bees might not simply store each flower type they have encountered in the past with maximum accuracy," says Chittka. "Instead, a key feature of bee memory might be the ability to extract common features of multiple flower types and store shared characteristics."

All mixed up

Bees are not the only animals to make mix-ups. In one similar experiment from 1969, pigeons were trained to recognise two similar colours, and then developed a preference for an intermediate shade that they had never seen before. And Ghirlanda has trained chickens to distinguish between male and female faces, after which they came to prefer faces that were more masculine or feminine than any that they had previously encountered.

"We have ample evidence that fish and insects are prone to the same memory illusions," says Ghirlanda. "I have come to consider memory phenomena of this kind as ubiquitous."

Chittka does not think false memories are useful for the bees, but he says they could be a by-product of other helpful memory processes. "In humans, we recently discovered that false memories might be a side effect of an adaptive memory system – the ability to form rules and categorise objects by common properties," he says. "There is no question that the ability to extract patterns and commonalities between different events in our environment is adaptive."

People are particularly prone to certain types of false memories. "Humans frequently make prestige-enhancing errors," says Elizabeth Loftus of the University of California, Irvine. These kinds of errors occur when people remember themselves to have got better grades in their studies than they actually did, or believe they had voted in a past election when they actually hadn't.

"This might make us feel better about ourselves," she says. But she adds that she is yet to see any evidence that animals other than humans routinely make such self-aggrandising mistakes.

Journal reference: Current Biology, DOI: 10.1016/j.cub.2015.01.023

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6 things you're dying to ask about head transplants

Read about the proposed head transplant surgery? Here are answers to questions on the tip of your tongue. And no, we can't defrost all the cryogenic heads

Why are we calling this procedure a head transplant rather than a body transplant?

The head transplant moniker is partly a hangover from monkey and dog experiments of the last century. This was how the surgeons that carried out those experiments referred to the procedure, and it stuck.

Technically, calling it a body transplant would be more accurate because the head is representative of the person receiving the new body part. But be careful, it's not a whole body transplant. That term is usually used to describe a procedure in which the brain of one organism is transplanted into the body – and skull – of another.

By calling Sergio Canavero's proposed surgery a head transplant it makes it clearer that this involves the head and the brain inside.

What's the difference between brain and head transplants?

A brain transplant would involve removing the brain from the skull and placing it in a donor skull. It is more difficult than a head transplant because of the complex surgery to separate the brain and blood supply without damaging delicate tissue.

Could the transplant technique work for a cryogenically frozen head?

No. The proposed technique requires a healthy human head and brain. It is not yet known whether it is possible to "defrost" a cryogenically frozen head and resurrect healthy brain tissue.

Would the surgery be psychologically damaging?

Some people who have received face or limb transplants mourn the loss of their old body part or feel that their self image is conflicted. Studies show that inputs from our body, such as a heartbeat or rumbling stomach, can influence our will power, emotions and language. Who knows whether the person who comes out of the operating room would be the same as the one who went in.

Would there be any benefits apart from getting a healthier body?

If the recipient head is older than the donor body, they may get a rejuvenating boost. Infusions of young blood can raise physical endurance and cognitive function in older animals. A study is now seeing if young blood has the same effect on people with Alzheimer's.

I'm a registered organ donor. Could my body be used for this?

Each country has its own rules. In the UK, joining the register would not automatically allow your body to be used. "If a person needs something not specified on our forms, we would ask a potential donor's family to consent," says an NHS spokesperson. "We would only approach a family if the planned procedure had ethical approval."

Read more: "First human head transplant could happen in two years"

Leader: "Body swaps sound like fantasy, but pose real questions"

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