Imagine if each of the words in this article had their own taste, or the music you’re listening to played out as visual scene in your mind. For synaesthetes – a small proportion of people whose senses intertwine – this is the stuff of the every day. “Most people describe it as a gift,” says Jamie Ward, a neuroscientist at the University of Sussex in the UK.

Now, he and his colleagues have found a new form of synaesthesia – one that moves beyond written language to sign language. It is the first time the phenomenon has been observed.

“People with synaesthesia experience the ordinary world in extraordinary ways,” says Ward. In theory, any two senses can overlap. Some synaesthetes connect textures with words, while others can taste them.

More commonly, written letters seem to have corresponding colours. An individual synaesthete may always associate the letter A with the colour pink, for instance. This type of synaesthesia has been found across many written languages, prompting Ward’s team to wonder if it can also apply to sign language.

New sensations

They recruited 50 volunteers with the type of synaesthesia that means they experience colours with letters, around half of whom were fluent in sign language too. All the participants watched a video of sign language and were asked if it triggered any colours.

Of those that understood sign language, four of them did indeed associate colours with the signed letters – and the colour was the same as they saw for written letters. For example, those that see the letter A as pink also associate pink with the hand sign used for that letter.

However, those who didn’t understand sign language did not report associating any colours with the gestures. This suggests that it is the meaning of letters and other symbols that is important for triggering other sensations – the action is not enough by itself.

Most of those in the study who knew sign language were not hard of hearing, and had learned to sign in later life. This suggests that their synaesthesia had adapted to this new form of language, says Ward. “It tells us that synaesthesia is not fixed in early life – exposure can bring new synaesthesia,” he says.

“The results demonstrate that this generalisation is not limited to spoken languages, but also occur in a manual language,” says Anina Rich at Macquarie University in Sydney, Australia. “The results are consistent with the idea that synaesthesia is predominantly mediated by conceptual links.”

Source: New Scientist