Synaesthesia is a neurodevelopmental condition affecting ~1% of the population. The word synaesthesia comes from the Greek syn (union) + aisthaesis (sensation), and the symptoms are often described as a ‘mixing of the senses'. It was first described by Sir Francis Galton in the journal Nature in 1880. Synaesthesia is characterised by altered sensory perception. In many cases, a sensation in one sensory modality triggers an automatic response in a different modality, as in auditory-visual synaesthesia, where sound triggers the perception of colour. For other synaesthetes, the synaesthetic response may occur in a different facet of the same sensory modality, as in visual grapheme-colour synaesthesia where reading black text triggers the perception of colour. Each sensory trigger is paired with a unique response, which remains consistent throughout the synaesthete’s lifetime – if middle-C = blue, it will always be that particular shade of blue.
Synaesthetic perception occurs simultaneously with ordinary perception, and can theoretically involve any pair of senses – however, almost all synaesthetic responses are visual. These percepts are most commonly described in terms of colours, but often involve visually salient texture, movement, and a particular layout in the synaesthete’s visual field.
As normal and abnormal percepts occur simultaneously, synaesthesia often results in perceptual and cognitive dysfunction. Cognitive interference from the synaesthetic percepts leads to difficulty with numerical and linguistic processing; numerical cognition is particularly affected. In extreme cases, synaesthetes may find their percepts overwhelming, necessitating isolation from the outside world to avoid sensory overload. Interestingly, synaesthesia has also been implicated in ‘positive’ cognitive variations, including enhanced recall and absolute (perfect) musical pitch. While we conduct our synaesthesia research under the umbrella of the ARC, it’s important to point out that there is not any known connection between synaesthesia and autism, though this is something that we are currently investigating.
In addition to having particular relevance for synaesthetes, synaesthesia offers valuable insight into normal cognitive development. Patterns observed in synaesthetic sound-colour and grapheme-colour pairings have also been observed to a lesser extent in non-synaesthetes, implying that synaesthesia stems from mechanisms common to all humans.
Our work focuses on the genetics of synaesthesia, with a particular emphasis on auditory-visual synaesthesia. Working in collaboration with other groups in the field, we aim to identify and characterise genes that may make people more susceptible to developing synaesthesia and to further clarify the role of genes in human cognition and perception.
As part of this work we have also developed an improved diagnostic instrument (the Revised Test of Genuineness, TOG-R), which can be used with any form of synaesthesia that generates visual percepts. We are happy to make the TOG-R available to researchers who wish to use it in their work.
In 1989, Professor Simon Baron-Cohen and Dr John Harrison founded the International Synaesthesia Association (now known as the UK Synaesthesia Association), the world’s first organisation dedicated to the synaesthesia community, with the aim of bringing synaesthetes and researchers together and facilitating the exchange of information and ideas. In 1995, an American sister organisation, the American Synaesthesia Association, was founded by Carol Steen and Patricia Lynne Duffy. There are now synaesthesia associations in Australia, Germany, Belgium, and Germany.
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