The name Samantha tastes like bubblegum

“The number 4 is a bright acid-yellow and 5 is crayola-blue. Together they should make 8, which is a bright green, but instead they really make 9, which is wet-dirt-brown. It has never made sense to me. Algebra is what makes X turn brown, too. Letters least of all should be brought into that mess.”

If you are like me, this will undoubtedly not make any sense to you. However, to approximately one in twenty people it may, at least to a certain degree, seem familiar, even if they may disagree vehemently on the exact pairings of colours and numbers. The above quotation is the writing of a sixteen-year-old girl with synaesthesia. Synaesthesia (syn meaning ‘together’ and aisthesis, ‘sensation’) is a neurological condition in which an instant, involuntary co-occurrence of one sensation takes place as a result of the occurrence of another type. This can happen between any of the senses – days of the week may have their own particular colours, G-major a particular smell, and a triangle a specific taste.

While the concept of synaesthesia is not new – ancient Greek philosophers already investigated the link between colour and music, and Newton suggested that colours and sounds may have similar frequencies – it was not until the 1980s that scientists started investigating synaesthesia in earnest.

Those without synaesthesia may wonder whether it is simply a set of made-up or delusional associations. However, one of the characteristics of synaesthesia is that pairings between sensations remain stable over time (life-long). Moreover, these sensations seem to arise from an organic basis: patterns of activity in a synaethetes’ brain reflect both the appropriate and the paired sensation as if it ‘really’ perceives both types of stimulation. For example, while anyone’s auditory cortex will be activated when listening to music, a sound-colour synaesthete will also activate the visual cortex to reflect the colours simultaneously experienced in their mind. Further investigation into synaesthetes’ brains has led to the discovery of ‘hyperconnectivity’, namely the existence of many more pathways between the cortical regions that process different sorts of sensory information as compared to a normal brain, maybe allowing more possibility for crossing-over of different sorts of sensory information.

Behavioural studies in babies have shown that our brain is hyperconnected at birth and that, as part of the maturation process, we lose this hyperconnectivity in the first few month to years of our life. Although a specific gene has not yet been discovered, synaesthesia tends to run in the family, and this has led researchers to believe that a genetic abnormality prevents the brain from complete cortical maturation, thus leaving the brain hyperconnected.

Even though synaesthesia is a neurological condition, it is difficult to claim that that people suffer from it. Many highly creative people such as Nabokov, Kandinsky, and Messiaen were synaesthetes, and for most it is just as innate as the colour of their eyes and the size of their feet. This ‘normalness’ of the condition may well be the reason why prevalence in the general population has been estimated from anywhere between 1 in 20000 to 1 in 20 people (the latter being a more likely estimate).

Although this may still leave the vast majority of us without such abilities, it is often overlooked how much we all possess some synaesthetic abilities. For instance, Professor Charles Spence of the University of Oxford showed in an experiment conducted at Heston Blumenthal’s award-winning restaurant that sounds play a particularly important role in our perception of food: a bacon and egg ice-cream was perceived as tasting more strongly of bacon when it was accompanied by the sizzling sound of bacon being fried compared to when there was no such sound present, the result of sensations crossing-over. Similarly, many of us automatically associate shapes and sounds (does “Kiki” sound sharp or “Bouba” rounded?) or even perceive certain names as being sexier than others. For fun exploring your own synaesthesic tendencies test yourself here.

As someone who does not have the slightest hint of a synaesthesic mind, I can only wish I could, if only for one day, return to my infant state and re-see the days of the week in vivid colour, let Kandinsky’s paintings make music in my mind, and finally find out what circles really taste like …

This post was written for and published on Cherwell's Matters Scientific