Uta Jurgens sees red whenever she swims the breaststroke. Backstroke is lavender, butterfly sky-blue. Jurgens, a graduate student at the Max Planck Institute for Brain Research in Frankfurt, Germany, has a form of synaesthesia in which the mere thought of a dip in the pool conjures up different colours.
According to Danko Nikolic, also at the institute, the discovery suggests that the traditional view of synaesthesia as a phenomenon directly triggered by sensory stimuli needs an overhaul.
"More and more research is suggesting that synaesthesia is not just triggered by sounds, smells, sights, or, as in this case, splashing around in a pool, but by the ideas and concepts that these sensory inputs evoke," he says.
In 2009, Hazem Toutounji, a national swimming champion for Syria, told Nikolic that each swimming style was bathed in a distinct colour in his mind's eye. Jurgens, a graduate student of Nikolic's, and a keen swimmer, admitted that her trips to the pool, too, were awash with colour.
To test their claims, Nikolic and colleagues showed Jurgens and Toutounji, plus a group of non-synaesthete volunteers, four black-and-white photographs of swimmers performing front crawl, backstroke, breaststroke or butterfly. Their task was to find the exact colour that the photos evoked in a book containing more than 5500 colours.
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A month later, Nikolic repeated the test. By assigning each colour in the book coordinates in a three-dimensional "colour space", he was able to calculate that the difference between the colours chosen on the two occasions was 8 times smaller for his synaesthetes than for non-synaesthetes.
Nikolic then performed a second experiment, known as a Stroop test. His team showed the group the same photographs with each photo printed in a different colour. The subjects were asked to name the colour of the photo as fast as possible. Both Toutounji and Jurgens took significantly longer to name the colour when it did not match the one evoked by their synaesthesia.
The first documented case of synaesthesia dates to 1812, when a medical student described the colours he saw when he heard music.
Since then, several forms of synaesthesia triggered by concepts rather than sensory information have been discovered. Some individuals associate colours with different days of the week, while others see the colours they associate with the number seven when presented with the numbers five and two together.
