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The Intrinsic Connections Between Synaesthesia and Language

Synaesthesia, which is literally defined as “joined sensation,” is a condition in which “an otherwise normal person experiences sensations in one modality when a second modality is stimulated” (Ramachandran & Hubbard, 2001, p. 4). Synaesthesia is most well known for the visual association of colors with numbers (grapheme-color synaesthesia), and is often dismissed as being unreal or irrelevant. Many common perceptions of synaesthesia are exaggerated to convey the phenomenon as an intense, hallucinatory experience. However, research by Ramachandran & Hubbard has suggested, “grapheme–colour synaesthesia is a sensory effect rather than a cognitive one or based on memory associations” (Ramachandran & Hubbard, p. 7). This is an important distinction when studying the link between synaesthesia and language.

Synaesthesia is a very real phenomenon with different levels of impact on those who experience it; “higher” synaesthetes experience a more intense degree of synaesthesia than “lower” synaesthetes. Most research on the phenomenon examines subjects who experience vivid and noticeable synaesthetic effects, and views synaesthesia as a somewhat mysterious sensory abnormality. However, a less prominent form of synaesthesia may exist on an exceedingly widespread and general scale. Human interaction with language is filled with synaesthetic undertones, and while this may not be the most apparent and commonly researched form of synaesthesia, especially in individual case studies, it can be theorized to be innately present on a universal scale. Many philosophers, linguists and scientists alike have found connections between synaesthesia and language.

Ludwig Wittgenstein, whose philosophical arguments primarily concerned language and communication, alludes to the idea of synaesthesia, stating, “If I say, ‘For me the vowel e is yellow,’ I do not mean: ‘yellow’ in a metaphorical meaning – for I could not express what I want to say in any other way than by means of the concept of yellow” (Wittgenstein, 1953, p. 228). Similar references to synaesthesia can be found throughout Wittgenstein’s Philosophical Investigations. A 1987 study of synaesthesia states, “…there is evidence that it [synaesthesia] represents something much more general, perhaps even universal, than an idiosyncrasy peculiar to a small number of people. Rather than being ‘abnormal,’ synesthetic perception may rest on a universal undercurrent of cross-modal equivalence” (Marks, Hammeal, Bornstein & Smith, 1987, p. 3). This argument can be improved upon by examining the way in which synaesthesia can be linked to the evolution of language, human use of metaphor, and phonosemantics, or sound-symbolism.

The first indication that synaesthesia may be linked to the evolution of language lies in the kiki/bouba effect. Developed by Wolfgang Köhler in 1929, the experiment dealt with the theory of sound-symbolism, which is “based on the shape of the lips (open and round vs. wide and narrow) when producing labels for certain objects” (Kovic, Plunket & Westermann, 2010, p. 20). The experiment involved presenting participants with two shapes; one had sharp, jagged edges and the other was rounded. Participants were told that in a Martian language, the two shapes were identified as either “kiki” or “bouba”. 95% of participants guessed that “kiki” was the object with sharp edges, and “bouba” was the rounded object. It can be concluded that these nearly unanimous results are due to the way that “sharp changes in visual direction of the lines in the right-hand figure [the object with jagged edges] mimics the sharp phonemic inflections of the sound kiki, as well as the sharp inflection of the tongue on the palate” (Ramachandran & Hubbard, p. 19). In other words, this incidence of sound-symbolism was caused by a link between sensory cortical areas and motor areas in the brain.

Another example of sensory-to-motor synaesthesia is dance, in which the rhythm of the movements synesthetically parallels the rhythm of the music. The application of this sensory-to-motor synaesthesia in the kiki/bouba experiment also “suggests that there may be natural constraints on the ways in which sounds are mapped to objects” (Ramachandran & Hubbard, p. 19). It has even been speculated that such cross-modal connections may have had such an immense influence that they constrained the evolution of language (Kovic, et. al., p 20). Additionally, the kiki/bouba experiment was conducted between both English and non-English speaking participants, further supporting the belief that such sound-symbolism is inherent among all humans rather than being a learned behavior. From this emerges the idea that synaesthesia affects common language processing on an undeniably intrinsic level.

It can be suggested that the phenomenon of synaesthesia is present in childhood development of language processing (Hunt, 2005). A 2008 study demonstrated that “3-year old children are able to generalise the meaning of novel sound-symbolic words, but not of non-sound-symbolic words, in a verb learning task” (Kovic et. al., p. 20). This provides parallel conclusions to the kiki/bouba study, except at a very young age. Another indicator of synaesthesia’s presence in children’s development of language processing is “kinaesthetically expressive mirroring of the physical world sometimes called ‘childhood animism’,” which is most present between the ages of two and four, and manifests in the form of impulsive statements such as calling a spilled glass of milk a “poor sad glass” (Hunt, p. 32). Yet another indicator is “‘what Piaget (1963) called word realism’ — the tendency to understand the word sound as fused with its referential object” (Hunt, p. 32). Word realism, while not equated to sound-symbolism, is still related, and generally disappears around the age of five or six.

Both childhood animism and word realism could be considered synaesthetic associations, and are extensions of Vygotsky’s account of “inner speech” – the nonsocial, egocentric childhood tendency to speak verbal thoughts out loud (Hunt, p. 33). Such traits among children are far too widespread and intrinsic to be attributed to environmental or learned factors; further proving that synaesthesia is likely to be universally present.

While inner speech is associated with the development of language processing in children, its importance is not limited to childhood experiences. Piaget believed that inner speech was only relevant during childhood and later disappeared as children matured into adults and developed social skills. If Piaget’s theory were correct, this would dismiss the belief that such synaesthetic childhood tendencies could be linked to adult synaesthesia. However, Vygotsky dispelled Piaget’s theory and instead showed that inner speech did not simply disappear but remained present and rather became internalized as children matured into adults. A 1920s study by Wheeler and Cutsforth found that higher level synaesthetic adults described their complex word-color associations as combined states of semantic meaning; in other words, their synaesthetic experiences were adult manifestations of their own forms of inner speech (Hunt, p. 34). From this it is evident that childhood synaesthetic associations are not simply lost with maturity but continue into adulthood on a different scale. Even more specifically, word realism can re-emerge in adulthood in the development of art forms such as poetry and music, and can be key in sense of meaning (Hunt, p. 32). It can be deduced that, not only does synaesthesia have an innate role in childhood language processing, but also that it may be carried into adulthood.

Imaging studies have shown us that the color areas in the brain are located in the fusiform gyrus, and that the visual grapheme area is adjacent and also located in the fusiform area. Ramachandran & Hubbard did not believe this to be a coincidence and proposed that, due to the proximity of such areas coupled with the prevalence of grapheme-color synaesthesia, cross-wiring is an extremely probable cause of synaesthesia. Additionally, synaesthesia is more common in children, likely due to the fact that there are “substantially more connections between (and within) areas than are present in the adult brain” (Ramachandran & Hubbard, p. 9). This means that cross-wiring in the brain is more prone to manifest in young children. While some of these connections are removed during maturation through a process of pruning, some remain intact. Ramachandran & Hubbard suggest that these remaining cross-modal connections may be the basis for synaesthesia; this maintains that synaesthesia begins in childhood and continues into adulthood on a lesser scale. This is also consistent with Vygotsky’s belief that inner speech becomes internalized as a child matures rather than disappearing in adulthood.

It is suggested that “an underlying synaesthetic capacity earlier in development might be required for the gradual development of metaphor” (Hunt, p. 37). From this, the connection between metaphor and synaesthesia begins to emerge. A metaphor is defined as “a figure of speech in which a word or phrase literally denoting one kind of object or idea is used in place of another to suggest a likeness or analogy between them” (Miriam Webster Dictionary, 2011). The ability to translate metaphorical meaning is a basic and essential concept of language processing. Metaphors are used commonly in everyday language, are prevalent in lyrics and poetry, and are driven primarily by sensory forms of symbolism. A 1987 study states:

When cross-modal similarities appear in language, they typically take the form of similes or metaphors. The cross-sensory or synesthetic expression provides one of the simplest kinds of metaphoric language, in which one mode of sensory or perceptual experience transfers to another. "Bright" and "dim," for example, are adjectives denoting levels on a dimension of visual experience; the one might characterize the strong illuminating effect of sunlight or the dazzle of the sun itself directly viewed, the other the paler illumination by moonlight or the weak glimmer of a distant star. To characterize a light as bright is to employ a literal description; to characterize a sound as bright, however, is – or at least may be – to use a cross-sensory metaphor. (Marks et. al., p. 1)

This description of cross-sensory metaphor is consistent with the phenomenon of synaesthesia, and the theory that it can be attributed to some level of cross-wiring in the brain (Ramachandran & Hubbard, p. 8).

In 1987, a study was performed to assess the comprehension of verbal, or metaphoric, modes of synaesthetic similarities. The experiment consisted of over 500 children between the ages of three and thirteen and over 100 adults, and participants were asked to match pitch to brightness. According to the results, “even 4-year-old children showed at least some capacity to translate meanings metaphorically from one modality to another (e.g., rating ‘low pitched’ as dim and ‘high pitched’ as bright)” (Marks et. al., p.v). Metaphor can thus be considered a verbal culmination of synaesthesia, and an inherent trait in language processing that is present in some form in humans of all ages.

While this sensory phenomenon is primarily considered to be abnormal in individuals, the evidence that synaesthesia itself is universally and naturally occurring is overwhelming. In those with higher levels of cross-modal associations, it is merely the intensity of synaesthesia that is abnormal. Analysis of the evolution of language, childhood language development, metaphor, and inner speech in adults, is indicative of synaesthesia being an underlying but crucial piece in the puzzle of language.


Hunt, H. T. (2005). Synaesthesia, Metaphor and Consciousness: A Cognitive-Developmental Perspective. Journal of Consciousness Studies, 12(12), 26-45. Retrieved from EBSCOhost.

Kovic, V., Plunkett, K., & Westermann, G. (2010). The shape of words in the brain.

Lawrence E. Marks, Robin J. Hammeal, Marc H. Bornstein and Linda B. Smith (1987). Perceiving Similarity and Comprehending Metaphor. Monographs of the Society for Research in Child Development. Vol. 52, No. 1

Ludwig Wittgenstein. (1953). Philosophical Investigations. Blackwell Publishing.

Metaphor. Merriam-Webster Dictionary. Retrieved from https://www.merriam-webster.com/dictionary/metaphor

Ramachandran & EM Hubbard (2001). Synaesthesia -- A window into perception, thought and language. Journal of Consciousness, 8, 3-34.