There’s Something About Zero

At this point, you may be shaking your head along with the behaviorists and saying, “This is all very interesting, but what use is knowing about synaesthesia?”

There are several answers to this one. The first is probably the most obvious: studying the brain in atypical states can tell us how it functions in its usual state. While synaesthesia is not a mental illness – indeed, most synaesthetes are very happy to have it – it is unusual. In the same way that injury to a specific part of the brain can tell us what goes on in that part, usually by its absence, synaesthesia can tell us what goes on in the areas of the brain that are involved in it. We don’t yet know precisely which areas these are, and they are likely to be different for each form of synaesthesia, but we’re getting there (e.g. Sperling et al., 2006; Rich et al.,2006).

The second explanation is a little less intuitive, and has to do with qualia – irreducible properties of a stimulus, such as redness. For most people, zero has only one quale, its “zeroness”, but for someone with number-color synaesthesia, zero can be just as black as it is zero: the two are not separable. Qualia are mysterious because they are completely private sensations, but synaesthesia offers us a window into their strange world.

There are other uses of synaesthesia research, but (as is appropriate for a social psychology magazine) I have chosen a final use that has social applications. Most people still aren’t aware of synaesthesia, and so it’s frustrating for children who have it to be told that they are lying, or worse, psychotic (Day, 2005). The better synaesthesia is understood, and the more widespread knowledge about it becomes, the lower the chances of this happening. If someone tells you that an insect sting is jagged orange, that a cake smells dome-shaped, or the word “magical” is green, don’t brush their words aside as mere metaphor. They probably have synaesthesia.


Cytowic, R.E. (1993). The Man Who Tasted Shapes. Cambridge: MIT Press.


Day, S. (2005). Some Demographic and Socio-cultural Aspects of Synaesthesia. In Robertson, L.C. and Sagiv, N. (Eds) (2005).Synesthesia: Perspectives from Cognitive Neuroscience. Oxford: UP.

Dixon, M.J., Smilek, D. and Merikle, P.M. (2004). Not all synaesthetes are created equal: Projector versus associator synaesthetes. Cognitive, Affective and Behavioural Neuroscience, 4, 335-343.

Larner, A.J. (2006). A Possible Account of Synaesthesia Dating from the Seventeenth Century. Journal of the History of the Neurosciences, 15, 245-249.

Ramachandran, V.S. and Hubbard, E.M. (2001b). Synaesthesia – A Window Into Perception, Thought and Language. Journal of Consciousness Studies, 8, 3-34.

Rich, A.N., Williams, M.A., Puce, A., Syngeniotis, A., Howard, M.A., McGlone, F. and Mattingley, J.B. (2006). Neural correlates of imagined and synaesthetic colours. Neuropsychologia, 44, 2918-2925.

Sagiv, N., Simner, J., Colins, J., Butterworth, B. and Ward, J. (2006). What is the Relationship between Synaesthesia and Visuo-Spatial Number Forms? Cognition, 101, 114-128.

Simner, J. and Hubbard, E.M. (2006). Variants of synesthesia interact in cognitive tasks: Evidence for implicit associations and late connectivity in cross-talk theories.  Neuroscience, 143, 805-814.

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