3 Early Scientific Descriptions of Synesthesia

A synesthesia-like phenomenon was first mentioned in 1690 by John Locke in his text An Essay Concerning Human Understanding. He described a blind man who associated the color scarlet red with the sound of a trumpet.[1] In 1720, the ophthalmologist T. Woolhouse also described a blind man who could hear and feel colors (Wellek 1937).

In 1812, the physician G. T. L. Sachs published a report on two albinos who perceived sounds and numbers in color. However, to this day it has not been possible to establish a connection between synesthesia and albinism (Ione and Tyler 2004).

In 1873, J. A. Nussbaumer announced through the medical weekly Wiener Medizinische Wochenschrift that he was a color-sound synesthete, hoping that this would perhaps call forth people who had made similar observations, as his self-description fundamentally contradicted the prevailing theory of a specific energy of the sensory nerves (according to Johannes P. Müller 1826). Encouraged by this description, in 1881 the psychiatrist Eugen Bleuler, himself a synesthete, published a first quantitative study of synesthesia in which he classified 12% of the 600 participants as synesthetes (Bleuler and Lehmann 1881) and provided detailed descriptions of these seventy-seven persons. This also enabled him to compare synesthetic perceptions with one another. He determined that inter-individually, photisms differ widely and yet share certain similarities. High notes, for example, tend to activate bright colors. Bleuler also ruled out that these perceptions could be learned, and he identified the brain as the original source. Further scientific papers were published in 1880 (Visualised Numerals) and in 1883 (Inquiries into Human Faculty) by Sir Francis Galton, a cousin of Charles Darwin.

The term synesthesia was probably first used in 1866 by the French physiologist and neurologist Alfred Vulpian, though with a different meaning than is common today.[2]

Locke’s essay does not deal with synesthesia in a neurological sense. For this, cf. Kevin T. Dann, Bright Colors Falsely Seen: Synaesthesia and the Search for Transcendental Knowledge (New Haven: Yale University Press, 1998), 8–9. The example of the blind man, which comes up several times in Locke’s essay, is used within the scope of a question related to perception theory. Following an empirical approach, Locke argues that mental pictures are necessarily based on sensory-specific perceptions. A blind man who has never experienced the sensory quality of scarlet red has no notion of this color whatsoever and accordingly attempts to understand it by forming a linguistic analogy (sound of the trumpet). John Locke, An Essay Concerning Human Understanding, Book 3, Chapter 4 (London, 1690), available online at