Blue or black? Science says it depends on sleep
NEW YORK When Cecilia Bleasdale posted a photograph online of a black and blue dress she was thinking of wearing to a wedding the pic went viral.
Some people saw the dress as white and gold, while others looked at the same image and thought it was blue and black. And only now have experts got a theory about what was going on: the way you interpret the picture depends, in part, on when you normally wake up.
‘‘For years the colour vision community was a very sleepy, stale, unexciting field,’’ says professor Pascal Wallisch, from New York University. ‘‘ We thought we had figured it out, that there were subtle differences but by and large people all saw the world the same.’’ The dress, though, ‘‘was like if geographers suddenly discovered a new continent’’.
Wallisch conducted a survey of 13,000 people to determine what assumptions and conditions might cause one person to see it as gold and another as blue.
He found that the ambiguity of the lighting on that late winter afternoon was crucial, leaving the dress poised between looking as if it was in shadow, in daylight or in artificial light.
‘‘If the brain faces uncertainty, in general it doesn’t say, ‘I don’t know’. It says, ‘I’ll fill in the uncertainty with assumptions’,’’ says Wallisch. ‘‘People made different assumptions.’’
Among those who thought the dress was backlit and in shadow, 80 per cent saw it as white and gold. ‘‘Why? Because shadows are blue, and so your brain subtracts blue light from the image.’’ That left it looking yellow.
The brain makes a similar adjustment to the bluish light of natural daylight, so people who assumed that the photo was taken outside were also more likely to see the dress as white and gold.
Wallisch thinks that maybe the critical factor for these assumptions is the light people are used to, which depends on their sleeping habits.
‘‘There are owls like me who get up very late and stay up very late, who get less daylight exposure. There are larks who see less artificial light.
‘‘Everything else being equal, on average I’d predict larks to see it as gold, owls as blue.’’ The Times