Wednesday Is Indigo Blue – Discovering the Brain of Synesthesia

by Richard E. Cytowic and David M. Eagleman
The MIT Press, London, England, 2009
309 pp. Trade, £19.95
ISBN: 978-0-262-01279-9.

Reviewed by Florence Martellini

martellini@btinternet.com

New technologies and the resurgence of interest in consciousness have combined to make synesthesia a research field of its own at the beginning of the 21st century, and in this book researcher Richard Cytowic and neuroscientist David Eagleman explain the neuroscience and genetics behind synesthesia’s multisensory experiences.

Synesthesia as an established field of scientific research is recent despite the fact that it has fascinated a wider public for decades. Even though synesthesia is evident at an early age, synesthetes often discover by accident their different perception of reality and, in most cases, are not taken seriously, in particular by the sceptical scientists who tend to believe that they simply speak metaphorically, like poets or artists with vivid imagination. Yet, synesthesia occurs in one in twenty people, and is even more common among artists––British painter Hockney only discovered later in his life when he had to design costumes and stage sets for the Ballet de Marseille and the Glyndebourne and Metropolitan Operas, that he had sound, colour, shape synesthesia. Illustrating with clear examples and definitions the reader can easily comprehends through the first pages what synesthesia is and the issues around its study and understanding.

Synesthesia is biologically based in genes and brains but in most cases requires early life exposure to culturally learned artefacts such as graphemes, colours, food categories, time units, etc. It does not appear to be switched on at birth but rather becomes evident as children acquire skills and tends to disappear with age, leading the authors to argue that synesthetic perception may be a normal stage of brain development that consciously persists in a minority of adults. Across the first seven chapters, the five common synesthesia types are reviewed and well illustrated with case studies - i.e. number forms, coloured letters (both written and spoken), tasted words, coloured hearing and the personification of letters and numbers – followed by the more unusual types of synesthesia. The authors also relate cases of individuals who express signs of multiple kinds of synesthesia “polymodal”, arguing that the gene may be active in a number of different areas of the brain simultaneously.

In chapter eight, by exploring the phenomena of metaphor and creativity, the authors cleverly draw parallels with non-synesthetes who have experiences of reality similar to that of synesthetes, hence, opening the way to lay out key features which link synesthesia with creativity. They also show the ways in which synesthesia can help us deepen our understanding of the neurological basis of metaphor, the kind of arts synesthesia inspires and what it tells us about creativity.

Chapter nine starts with a very good insight into the ways in which the brain is organised and functions. However, the authors challenge the concept that the brain is merely made up of modules and that given discrete functions operate in separate channels because synesthesia contradicts this existing theory. They argue that synesthesia is not localized in any one spot of the brain, rather, it is a cross talk between several brain areas, all of which contributing to the synesthetic experience. It exists as the dominant process in the distributed network at a given time. And the difference between synesthetes and non synesthetes brains is not whether cross talk exists but rather its degree, of which variation still needs to be determined - depending on both genetics and learning over a lifetime, there are a number of possible combinations in which brain areas may interconnect. But how does this cross talk come about? One claim is that connections are there automatically in everyone but they do not necessarily function.

Synesthesia, in its dozen of varieties, highlights the differences in how individuals subjectively see the world, reminding us that each brain uniquely filters what it perceives. Hence, reality is more subjective than most people realize and synesthesia is a window into the mind and brain, and the differences in the ways in which people experience the world.

Overall, this book is a very clear and comprehensive synthesis of the progress of the field of synesthesia, thus, of interest to experts and lay people curious about neuroscience and/or creativity. It highlights the ways in which synesthesia can enrich and open out current understanding of the brain and, consequently, man’s perception of reality. Its authors bring out, though, that neuroscience is only at the very early stage of its journey into the discovery of the human brain.