Synaesthesia is where the senses are ‘crossed’ so people might experience visual figures, such as letters, as tastes. This is one type, but letter to colour, sound to colour or number to space are most common.
This new study was initiated when the researchers were testing people with other forms who synaesthesia who happened to mention that they could ‘hear’ a moving pattern on a computer monitor.
Neurophilosophy picks up the story where the researchers sought to confirm this with an elegant experiment:
Saenz and Koch devised a task which could be used to objectively confirm the reports of the 4 participants, a task on which they would out-perform non-synaesthetes who do not experience the “extra” sensation. The task involved judging rhythmic patterns – in each trial, the participants were presented with pairs of sequences of either visual flashes or auditory beeps, and then asked if the two were the same.
Typically, non-synaesthetes are much better at judging auditory than visual sequences. But the hearing-motion synaesthetes should be at an advantage when presented with sequences of visual flashes, because they can hear, as well as see, the pattern. This is exactly what was found: the 4 synaesthetes and the 10 non-synaesthete controls performed equally well in the trials of sound sequences, with an accuracy of around 85%. But in the trials with sequences of visual flashes, the synaesthetes remained accurate, with a score of about 75%, whereas the performance of the controls fell to 50%, which is what would be expected by chance.