Experts from Bradford and Giessen add some colour to the dress debate

In the days following publication of “The Dress“ psychologist Karl Gegenfurtner from the University of Giessen in Germany and Marina Bloj from the University of Bradford in the UK, carried out an experiment asking 15 people to view the photograph on a well-calibrated colour screen under controlled lighting.

Professor Marina Bloj, Professor of Visual Perception within the Bradford School of Optometry and Vision Sciences at the University of Bradford, said: “When the dress saga started I was visiting my colleagues in Germany to develop some new colour vision experiments and we had an ideal opportunity to use the set-up to do some rigorous studies on this polemical image.

“The confusion would have never occurred if it was not for the special colours present in the photograph, it would not have happened with other coloured dresses. The bluish and yellow colouring in the image correspond to colours that we experience naturally during the course of the day, they lay on what is known as the daylight locus.

“We can normally discount this illumination effect, but the in the case of #TheDress not enough information is available in the photograph so different people make unconsciously different assumptions and as a result perceive the dress differently. Some see it as a blue dress under warm light, others as a white dress under cool illumination.

As part of the experiment the team adjusted the colour of a disc to correspond to the colours the participants saw in the photograph. Participants reported seeing a continuous range of shades from light blue to dark blue, rather than the two dominant colours reported so far - white and blue.

The question should thus not be whether the dress is blue or white, but whether it is light blue or dark blue,” says Prof. Dr. Karl Gegenfurtner, department of psychology at Justus Liebig University Giessen (JLU). “Despite the continuous choice of matching colours, observers are consistent in calling the dress ‘white’ when their match lies above a certain brightness and ‘blue’ when it lies below.”

The team discovered that all test subjects basically perceived similar colour shades, only varying in lightness. These perceived colours have something in common, they all are part of the so-called daylight locus; depending on the position of the sun during the course of the day, daylight tends to be rather bluish (at noon) or rather yellowish (in the morning and in the evening).

Marina said: “Usually, people are able to unconsciously filter the effect of bluish or yellowish light with the result that everyone perceives the same colours. To do so, we require reference points, otherwise known as colours, which are located outside the daylight locus. However these colours (generally red or green) are completely missing in the case of #TheDress. Therefore, the photograph does not provide relevant information on the scene’s luminance levels.”

Various studies have proven that people have difficulties perceiving colours along the daylight locus correctly. Test subjects are for instance rarely able to set a completely neutral grey on the screen without tending to a slightly bluish or yellowish tinge. Deviations concerning red or green tendencies on the contrary hardly ever occur, which, in turn, explains why a red and green colouring of the dress on a screen would look the same colour to participants.

The research results will be published in the journal “Current Biology”

Article

Karl R. Gegenfurtner, Marina Bloj and Matteo Toscani: The many colours of ‘the dress’, Current Biology 25, R1–R3, June 15, 2015

DOI: 10.1016/j.cub.2015.04.043 http://dx.doi.org/10.1016/j.cub.2015.04.043

Images

The original photo which puzzled social network users. Image: swiked/Tumblr (Reproduced with permission from Cecilia Bleasdale)

Cross check with a reddish coloured dress. Montage: Gegenfurtner et al. / Current Biology 2015