A guest post by neuroscientist and synaesthesia specialist Thomas Wright from the University of Sussex on just how he found himself in a muddy field with a singing brain.

Picture the scene if you will. I’m in a hot, stuffy cupboard hunched over a computer. Behind me are Jen (from Guerilla Science), Mink and Doc (both from Coney) and Jamie (my supervisor, by now quite nervous). A webcam hangs limply from Doc’s hand and the speakers are ominously quiet. Nobody has made the trip down to Brighton for this.

Which is why, when the software suddenly, imperiously, decided to jump into life, I think I may have giggled with relief.

Weeks earlier, my lab group had been contacted for advice on how to create a game exploring a phenomenon called synaesthesia, whereby two senses become entwined.

The idea: to produce a computer program that would have synaesthesia so festival-goers could experience the condition (without the need for hallucinogenic substances).

Unbeknownst to Guerilla Science though, I was already working on a program that would do just this. Apart from the fact that my version is for blind people rather than festival-goers, that first email from Coney contained an uncanny description of my day-to-day research: They wanted to build an “artificial brain machine which turns visual input into music” – and I study systems for blind people which convert visual input into sounds.

It seemed like a match made in heaven.

This explains why the six of us were meeting, although not why we were crammed into my cupboard-cum-laboratory (don’t ask). But this leaves one important question unanswered…

What, exactly, is synaesthesia?

Synaesthesia is, put simply, when a real-life stimulus in one sense (such as vision) triggers an perceptions in another sense (or even senses).

Synaesthesia is estimated to occur in one in 23 people, but can take a variety of forms. Colour-grapheme synaesthetes are people who perceive letters and numbers as coloured. Spatial-sequence synaesthetes associate numbers (or dates, or weights, or speeds – any sequence) with specific locations arranged around their bodies, so that the number 2 might hover over your left foot, whilst 10 might always sit in front of your nose.

And other synaesthetes hear sounds when they see colours; it was this form of synaesthesia that we wanted to artificially reproduce with a computer program.

Kandinsky described "symphonies of colour" and is now thought to have been a synaesthete.

“But hold on,” I hear you all cry, “everyone knows that blue is cold and zero is black. These so-called synaesthetes just have an active imagination!” Whilst it is true that we all share a loose set of cultural associations, for most people they are simply metaphors.

For true synaesthetes, the association is involuntary and consistent. They will automatically perceive a colour in response to a certain sound, for instance, with great reliability. Moreover, synaesthetes will perform better than non-synaesthetes at tasks that depend on their sensory associations. Colour-grapheme synaesthetes, for example, will be quicker to identify a shape made from “2”s hidden amongst “5”s because, for synaesthetes, the “2”s literally appear to be a different colour.

A synaesthete might see the different numbers as different colours (right), which would make it easier to determine that they make a triangle.

Shoot forward a fortnight from our tense rendezvous in the cupboard and you’ll find me in a lab coat, sat by some bales of straw, in a tent, in front of a giant foam brain. Being a scientist is great.

Alongside me are Professor Koch (aka Alyn Gwyndaf), Mink Ette and Simon Katan. In front of us: a gaggle of curious festival-goers eyeing up our giant eye with suspicion. The scene is set – we were ready to do science.

Thomas, with Professor Koch (pronounced the naughty way) to his left.

The eye and brain form our artificial synaesthesia machine, which produces different sounds according to the colours presented to it. The task for our audience was to teach the brain new colours and hence, new sounds. It was harder than it may seem, too, as what may appear like one colour to us could look like two to the computerised eye. For example, shadows and reflections both change the apparent colour of an object. This didn’t deter the costumed hordes at the Secret Garden Party from laying down in front of it or, in some instances, taking their clothes off to be used as sacrificial offerings.

A month later we had the opportunity for an encore performance at the Green Man Festival in Wales. This time the science wasn’t just going to be theatrical; we had prepared a mini-experiment that we unleashed upon the unprepared, unwashed, unwitting revelers. Between the two performances on Saturday and Sunday we went hunting for synaesthetes throughout the festival grounds.

Synaesthetes will always experience a particular sensation in response to a particular stimuli – the associated colour won’t change. So we used a laminated colour chart, some coloured letters and a battery-powered keyboard to sniff out people who exhibited this trait. We would present a stimulus (a letter or a musical note) and ask our participants to choose a colour. After repeating this with different stimuli, we repeated them with the friendly volunteers. By working out how consistent the chosen colours were for each person, we could estimate the probability of them being synaesthetic.

Using this high-tech method, we tested for colour-grapheme (using letters) and colour-sound synaesthesia (using the musical keyboard). In total, we managed to find three potential synaesthetes. Our tests also seemed to show trends and patterns: Among the people we tested the letter A, for instance, tended to be yellow. Higher pitched notes tended to be associated with lighter colours than lower pitched notes.

But don’t be fooled, the most scientifically relevant aspect of our micro-test were its flaws. For instance: people disproportionately opted for colours that were close to the edge of the colour charts. Because of our use of two different charts, this indicates that a selection bias may have been affecting our data.

Additionally, the interval between the first and second exposures was really too short. Nothing we couldn’t have predicted, but still an interesting demonstration of the rigour that good science demands.

If you think you might be a synaesthete, why not head to David Eagleman’s Synaesthesia Battery and, if you’re feeling generous, quote my colleagues email address: c.jonas@sussex.ac.uk.