The history of synaesthesia research

The first scientific reports derive from George Sachs in the year 1812. In his dissertation he describes his own synaesthesia[1]. In this time there was not a great interest on this issue[2]. When Sir Francis Galton, the cousin of Charles Darwin, reported about synaesthetes[3] the attention on this field raised. Some publication followed. The US-scientist Mary Calkins was the one who introduced the term "synaesthesia" at the and of 19th century[4]. Around 1930 the behaviourism gained importance in psychological science: Learning and behaviour were reduced on interactions with external influences. In this period many experiments in conditioning[i] where conducted. It was assumed that internal feelings and thoughts are not measurable. Therefore synaesthesia did not fit at all into the scientific approaches on this period and was forgotten for several decades. The lack of information about synaesthesia lead to the circumstance that synaesthetes were classified long time as "ill" [2], as „people with great fantasy", or as „Acid-Junkies" or „Pot-Heads"[5].
Richard E. Cytowic was one of the first which began to dedicate with synaesthesia at the end of the last millennium. Other scientists followed and synaesthesia gained more and more on importance and interest.
In this century a fascinating boom began. While at the beginning conclusions mainly were drawn by interviews with synaesthetes, nowadays there is a lot of empirical research: information is gained by experiments with synaesthetes and non-synaesthetes, statistical analysis and not due to statements of some single synaesthetes.

References:

1. Kron WO: Pseudo-chromaesthesia, or the association of color with words, letters, and sounds. In., vol. 5: American Journal of Psychology; 1892: 20 - 41.
2. Hochel M, Milan EG: Synaesthesia: The existing state of affairs. Cognitive Neuropsychology 2008, 25(1):93-117.
3. Galton F: Colour associations. In: Synesthesia: Classic and contemporary readings. Oxford: Blackwell; 1997: 43-48.
4. Ward J: The Frog who Croaked Blue: Synesthesia and the Mixing of the Senses: Routledge; 2008.
5. Ramachandran V, Hubbard EM: Synaesthesia - A window into perception, thought and language. Journal of Consciousness Studies 2001, 8(12):3-34.

Traduced from German to English by Tiffany Ebner