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Updated: May 19, 2026

Training Synesthetic Letter-color Associations by Reading in Color
Published on: February 20, 2014
[Synesthesia as a neuronal palimpsest]
1Centre de recherche cerveau et cognition (CERCO), université de Toulouse et CNRS UMR 5549, pavillon Baudot, centre hospitalier-universitaire (CHU) Purpan, BP 25202, 31052 Toulouse Cedex 3, France. jean-michael.hupe@cerco.ups-tlse.fr
Abstract:
Synesthetes, a small fraction of the population, experience systematic, additional associations. For example, they may arbitrarily associate a specific color to each letter or number. Synesthesia has offered for the last ten years to cognitive science a unique opportunity to study the neural bases of subjective experience, drawing on individual differences just like in neuropsychology, but with healthy people. Here we review the current knowledge and propose a new theory, the "palimpsest hypothesis", a variant of the recycling hypothesis for reading. The neural development of written language expertise (a recent cultural invention acquired without any genetic modification) requires indeed the recycling of brain regions predisposed to expertise acquisition into reading regions. The palimpsest hypothesis supposes that for synesthetes recycling involves neuronal networks that were already specialized for color perception. Synesthetic colors would be the remains of this former expertise.
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