Synaesthesia is a rare phenomenon in which real sensory experiences evoke sensory experiences that are not directly caused by outside physical events.
For example, when a synaesthete hears a name, it can experience certain taste unique for this particular name. For a synaesthete person, ‘John’ could always taste as chocolate. In one common form of synaesthesia letters and digits are associated with a concurrent perception of color. This phenomenon is known as grapheme-color synaesthesia. The illustration shows grapheme-color associations for one synaesthete who volunteered as a participant in our study.
We have conducted a number of studies conjointly indicating that synesthesia is not a sensory-sensory phenomenon, as it has been largely held. Instead, this is a semantic-sensory phenomenon in which the meaning of the stimulus induces perception-like experiences. Hence, I proposed that a more accurate name for the phenomenon is ideaesthesia, which is Greek for “sensing concepts” (Nikolić, 2009). The theory of ideasthesia is based on arguments for introducing a semantic component and on a proposal how the semantic system contributes to the phenomenon. The following figure illustrates the central role of concepts for the additional sensations in ideasthesia across different sensory modalities:
Studies – Empirical evidence
Immediate transfer of synesthesia to new graphemes: In one study we have been able to use the theory of ideasthesia and make novel experimental predictions, which in turn enabled us to create novel synaesthetic associations. In has been known that associations in grapheme-color synaesthesia are acquired in early childhood and remain robust throughout the lifetime. Also, it was known that synesthetic associations can transfer to novel inducers in adulthood as one learns a second language that uses another writing system. However, it was not known how long this transfer takes. The theory of ideasthesia predicted that grapheme-color associations should transfer to novel graphemes very quickly, within minutes. And this is what we have proven experimentally. We created novel synaesthetic associations after only a 10-minute writing exercise (see the illustration). Most subjects experienced synesthetic associations immediately after learning a new Glagolitic grapheme (Mroczko et al., 2009). Also, these associations generalized to graphemes handwritten by another person. The fast learning process and the generalization suggest that synesthesia begins at the semantic level of representation with the activation of a certain concept (the inducer), which then, uniquely for the synesthetes, activates representations at the perceptual level (the concurrent).
Learning a new graphical “language”: In another recent study we could show also that the process of choosing the colors for novel synaesthetic associaitons involves semantic processes. When faced with a novel meaningful symbol, synaesthetes often assign a color to it by using similarity judgments to other symbols: Symbols with similar shapes tend to be associated with similar colors (Jürgens and Nikolić, 2012).
Swimming-style synesthesia: We also discovered a new type of synaestheisa, dubbed Swimming-Style Synaesthesia. Here, each swimming style is associated with another color. We could show that phenomenon is also a case of ideasthesia. It is the concept of a swimming style that elicits the synaesthetic experiences. This synaesthesia does not require the proprioceptive information that arrives to the brain from being engaged into performing a particular swimming style (Nikolić et al., 2011). The figure below shows stimuli used to prove objectively the existence of swimming-style-synesthesia using a Stroop task.
How synesthesia comes about?
We have proposed (Mroczko-Wąsowicz and Nikolić 2014) that kids create synesthesia when they face a semantic vacuum. Semantic vacuum is when you cannot easily place new information within the existing knowledge in your head. For example, if you have to learn the word Raznolikost and you are being told that it means Variety, and you are not familiar with Slavic languages, you may have no existing knowledge to which you could “anchor” that new information. You may only learn the word from scratch, by applying a slow process of rote learning. This is a situation of semantic vacuum.
Using semantic vacuum hypothesis we have proposed an answer to the otherwise mysterious question of why graphemes and time units are the most common inducers in synesthesia. By some accounts these two groups of inducers are responsible for more than half of all synesthetic associations out there. But why these two? And why not others? The answer is that graphemes and time units present the kids in our civilization with the first concepts that require a semantic leap from a well-connected and sensory-rich world of concrete objects (e.g., toys) to a world of abstract mental tools that they will later need in adulthood (e.g., one needs a concept of Tuesday but it is impossible to see or feel a Tuesday). This brings the kids into a situation of a semantic vacuum. We propose that synesthetic kids cope with that vacuum by adding concrete sensory-like experiences to those abstract concepts (e.g., adding a color or a spatial location).
Ideasthesia and art
Every scientists hopes do discover something that serves not only as abstract knowledge but actually affects the society in some meaningful way. For that reason, it has been my great pleasure–in addition to being a complete surprise–to witness the concept of ideasthesia inspiring artists and, in some strange way, helping them understand what is it that they actually do.
A TED Ed educational movie on ideasthesia:
A lecture on ideasthesia at SoundThinking conference (YouTube):
Van Leeuwen T.M., Singer W. and Nikolić D. (2015)
The merit of synesthesia for consciousness research.
Front. Psychol. 6:1850. doi: 10.3389/fpsyg.2015.01850
Mroczko-Wąsowicz, A., D. Nikolić (2014)
Semantic mechanisms may be responsible for developing synesthesia.
Frontiers in Human Neuroscience 8:509. doi: 10.3389/fnhum.2014.00509
Jürgens, U.M. and D. Nikolić (in press)
Synaesthesia as an Ideasthesia – cognitive implications.
In: Synesthesia – Learning and Creativity. Edited by J. Sinha. Proceedings from the conference Synesthesia and Children. Learning and Creativity, Ulm, May 2012. Synaisthesis, Luxembourg.
Mroczko-Wasowicz, A. and D. Nikolić (2013)
Coloured alphabets in bi-lingual synaesthetes.
The Oxford Handbook of Synaesthesia. 165-180.
Rothen N., D. Nikolić, U.M. Jürgens, A. Mroczko-Wąsowicz, J. Cock, and B. Meier (2013)
Psychophysiological evidence for the genuineness of swimming-style colour synaesthesia.
Consciousness and Cognition, 22(1):35-46.
Nikolić, D. (2009)
Is synaesthesia actually ideaestesia? An inquiry into the nature of the phenomenon.
Proceedings of the Third International Congress on Synaesthesia, Science & Art, Granada, Spain, April 26-29, 2009.
Nikolić, D., P. Lichti and W. Singer (2007)
Color-opponency in synesthetic experiences.
Psychological Science, 18(6):481-486.