Show Hide image

The dress of many colours: is it blue and black or white and gold?

A recent debate on the colour of a dress has broken the internet. But is it all just a visual illusion? 

The infamous dress, in all its variety. Photo: swiked/Tumblr

The internet went Armageddon last night over the colour of an (let’s face it) ugly dress which Tumblr user swiked uploaded. The disagreement in colours divided the social media world: is it blue and black or white and gold or something in between?

Photo: swiked/Tumblr

(By the way, it’s clearly blue and black.)

When things start to question our existence we turn to science to tell us things are going to be ok. Let’s turn to how our brains translate colour through our retinas:

Visible light can be broken down into various wavelengths which correspond to different perceivable colours. This all depends on what colour(s) the object is reflecting. This reflective light enters through the eye lens and hits a light sensitive layer of tissue called retina in the back of the eye where a cascade of neural messages are sent to the visual cortex – the part of the brain that processes visual information. However, the quality of light that penetrates into our retina plays a big part.

Luminance is the intensity of light emitted from a surface per unit area of light travelling in a given direction. So the brain has to work out how much of the luminance (or lack thereof) is caused by the colour of the square and how much is caused by the shadows. “In the case of the dress, some people are deciding that there is a fair amount of illumination on a blue and black (or less reflective) dress. Other people are deciding that it is less illumination on a white and gold dress (it is in shadow, but more reflective),” said Cedar Riener, an associate professor of psychology at Randolph-Macon College in a BuzzFeed interview.

An example is the famous Adelson checkerboard optical illusion, in which square A and square B are same shade of grey: 

 

 

So why do different people’s brains interpret light differently? Humans have evolved to see in the daylight. Typical daylight extends from blue-white at noon to pinkish-red at dawn. Bevil Conway, a neuroscientist who studies colour at vision at Wellesley College told Wired: “What’s happening here is your visual system is looking at this thing, and you’re trying to discount the chromatic bias of the daylight axis. So people either discount the blue side, in which case they end up seeing white and gold, or discount the gold side, in which case they end up with blue and black.”

Conway also suggests that the white-gold or blue-black bias could be linked to whether we prefer daylight or night time. So those who perceive the dress as white-gold might be interpreting it as though it's in blue natural lighting, and those who perceive it as blue-black might be interpreting it as though it's in yellow artificial lighting. “I bet night owls are more likely to see it as blue-black,” Conway says.

Based on correct white-balancing, we can confirm that the dress is blue and black (sorry white and gold die-hards), but ultimately, visual perception is in the eye of the brain holder.

Luckily for the New Statesman, Ed Miliband established Labour's position on the blue-black and white-gold spectrum: 

Tosin Thompson writes about science and was the New Statesman's 2015 Wellcome Trust Scholar. 

Davide Restivo at Wikimedia Commons
Show Hide image

Scientists have finally said it: alcohol causes cancer

Enough of "linked" and "attributable": a new paper concludes that alcohol directly causes seven types of cancer.

I don't blame you if you switch off completely at the words "causes cancer". If you pay attention to certain publications, everything from sunbeds, to fish, to not getting enough sun, can all cause cancer. But this time, it's worth listening.

The journal Addiction has published a paper that makes a simple, yet startling, claim: 

"Evidence can support the judgement that alcohol causes cancer of the oropharynx [part of the throat], larynx, oesophagus, liver, colon, rectum and [female] breast"

So what's especially significant about this? 

First, scientists, unlike journalists, are very wary of the word "causes". It's hard to ever prove that one action directly led to another, rather than that both happened to occur within the same scenario. And yet Jennie Connor, author of the paper and professor in the Preventive and Social Medicine department at the University of Otago, New Zealand, has taken the leap.

Second, alcohol not only causes cancer of one kind – the evidence supports the claim that it causes cancer at seven different sites in our bodies. There was weaker evidence that it may also cause skin, prostate and pancreatic cancer, while the link between mouth cancers and alcohol consumption was the strongest. 

What did we know about alcohol and cancer before?

Many, many studies have "linked" cancer to alcohol, or argued that some cases may be "attributable" to alcohol consumption. 

This paper loooks back over a decade's worth of research into alcohol and cancer, and Connor concludes that all this evidence, taken together, proves that alcohol "increases the incidence of [cancer] in the population".

However, as Connor notes in her paper, "alcohol’s causal role is perceived to be more complex than tobacco's", partly because we still don't know exactly how alcohol causes cancer at these sites. Yet she argues that the evidence alone is enough to prove the cause, even if we don't know exactly how the "biologial mechanisms" work. 

Does this mean that drinking = cancer, then?

No. A causal link doesn't mean one thing always leads to the other. Also, cancer in these seven sites was shown to have what's called a "dose-response" relationship, which means the more you drink, the more you increase your chances of cancer.

On the bright side, scientists have also found that if you stop drinking altogether, you can reduce your chances back down again.

Are moderate drinkers off the hook?

Nope. Rather devastatingly, Connor notes that moderate drinkers bear a "considerable" portion of the cancer risk, and that targeting only heavy drinkers with alcohol risk reduction campaigns would have "limited" impact. 

What does this mean for public health? 

This is the tricky bit. In the paper, Connor points out that, given what we know about lung cancer and tobacco, the general advice is simply not to smoke. Now, a strong link proven over years of research may suggest the same about drinking, an activity society views as a bit risky but generally harmless.

Yet in 2012, it's estimated that alcohol-attributable cancers killed half a million people, which made up 5.8 per cent of cancer deaths worldwide. As we better understand the links between the two, it's possible that this proportion may turn out to be a lot higher. 

As she was doing the research, Connor commented:

"We've grown up with thinking cancer is very mysterious, we don't know what causes it and it's frightening, so to think that something as ordinary as drinking is associated with cancer I think is quite difficult."

What do we do now?

Drink less. The one semi-silver lining in the study is that the quantity of alcohol you consume has a real bearing on your risk of developing these cancers. 

On a wider scale, it looks like we need to recalibrate society's perspective on drinking. Drug campaigners have long pointed out that alcohol, while legal, is one of the most toxic and harmful drugs available  an argument that this study will bolster.

In January, England's chief medical officer Sally Davies introduced some of the strictest guidelines on alcohol consumption in the world, and later shocked a parliamentary hearing by saying that drinking could cause breast cancer.

"I would like people to take their choice knowing the issues," she told the hearing, "And do as I do when I reach for my glass of wine and think... do I want to raise my risk of breast cancer?"

Now, it's beginning to look like she was ahead of the curve. 

Barbara Speed is a technology and digital culture writer at the New Statesman and a staff writer at CityMetric.