Synesthesia and Metaphor: Between Fact and Fiction (VIDEO)

Philosophers have long debated the merits of using metaphor in conversation. But new neurological studies on synesthesia may shed some light on the issue.
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Most of us use metaphors frequently in conversation. "Your argument is clear." "Love is a game." "She has a sweet personality." But few of us stop to think about why we do this -- why do we so easily pair unlike categories? Are we simply being abstract? Is there some secret logic to this illogical way of talking? This question has recently sparked much debate in the social sciences, and new neurological studies on synesthesia may shed some light on the issue.

Synesthesia is the perception of two unlike sensory modalities at once. For example, some synesthetes report reading or hearing a name and instantly associating it with a color, gender, or taste. One synesthete reports that the name "Derek" consistently tastes like earwax. Another claims that letters have distinct personalities.

For a long time, synesthesia was thought to be a pathology. Over the last 20 or so years, however, it has been shown that synesthesia is indeed a perceptual reality. It is now estimated that 1 in 23 people experience some form of pronounced synesthesia. There are dozens of forms of synesthesia recorded. Synesthesia is more common in children than adults, as Cytowic and Eagleman report in their book Wednesday Is Indigo Blue (8, 122, 11). Latent (as opposed to pronounced) synesthesia is prevalent in a conservatively estimated 90 percent of the population -- as the Bouba Kiki effect demonstrates. "The difference between synesthetic and nonsynesthetic brains is not whether cross talk exists" Cytowic and Eagleman note "but rather its degree" (232). That tingly feeling you get when you hear music you like, or the fact that you salivate when you see salty food? Synesthesia.


Not only is pronounced synesthesia evidenced with surprising frequency in the population at large, but it is evidenced in all infants during the first weeks of life. Children are born into the world as "synesthetic knots." Their original perceptual experience is one of overwhelming perceptual unity, a unity that is slowly parsed into fixed associations and differentiation (Cytowic and Eagleman, 107). Daphne Maurer writes in The World of The Newborn: "the synesthetic confusion of those sensory signals does not confuse [the infant] as it would confuse us: since he does not know that voices do not have odors -- or that voices even exist apart from himself -- he is not confused when he smells a voice. Indeed, in the newborn's naive state, his synesthesia simultaneously confuses his world and simplifies it. It causes him to perceive the world not as an ordered set of discrete objects but as a single, multi various set of sensations -- a melange of sensations affecting every part of his body" (196).

It has recently been suggested that some metaphors are abstract associations, based on prerequisite subconscious associations or even sublated synesthetic perceptions (latent synesthesia). In fact, some forms of metaphor might be the "normal" or commonly shared representation of synesthesia (Cytowic and Eagleman, 2009). For example, Hubbard and Ramachandran argue: "We all speak of certain smells -- like [perfume as] -- being sweet, even though we have never tasted them. This might involve close neural links and cross-activations between smell and taste, which can be thought of as a form of synaesthesia that exists in all our brains" (Hubbard and Ramachandran, 2003).

So our initial "blended perceptions" emerge as certain equivalencies, some of them fixed and normative -- like smell and taste, or sight and shape, others "peripheral" or less useful. Some metaphorical identities might then emerge as "hypothetical" or abstract renditions of these peripheral options. This is represented abstractly, and is not perceived, though of course unconscious perception cannot be ruled out.

This new way of looking at metaphor somewhat complicates our tidy conceptual-perceptual distinctions. It forces thinkers to ask new questions -- for instance: how does our physical experience inform our concepts? Are all metaphors representations of once-physical experience (the answer to this question might be more complicated than we think -- check out the work of Lakoff and Johnson, for instance). How can metaphors be used in therapy? How do concepts and interpretation change the way we see the world? What about metaphors like "God is Love"?

Synesthesia is understood to be perceptually involuntary, but studies of adult synesthetes suggest that attention and conceptual import of perceptual categories affect the vividness of a synesthetic experience, as Cytowic and Eagleman report (74). For instance, word-color synaesthetes as well as word-taste synesthetes seem to be affected by the meaning of the word as well as the written or illocutionary presence of the word (70, 75). Thus, concepts affect the synesthetic experience. "For synesthetes", writes Cutsforth, "the picture is the meaning. they visualize the meaning ... images behaved as if they constituted fully conscious meanings" (92, 94). In other words, reasoning and visual perception are intimately connected for the synesthete. So we can perceptually reason. But can we reason our way into synesthetic perception? It seems that this might also be possible: one study found that "the most experienced meditators report concept-based or categorical-sensory amalgamations. That is, cognition such as 'emotions, thoughts, and images' are experienced in sensual terms such as sound, taste, or touch" (Cytowic and Eagleman, 221).

From both a philosophical and a scientific standpoint, and regardless of whether we think it's factual or fictional, the nature of metaphorical processing is as-yet largely undefined, and new questions are now being asked: what is the purpose of associating unlike things? What kinds of horizons does this process make possible?

What do you think?

Watch VS Ramachandran here, Dr. Richard E. Cytowic's presentation to the Library of Congress here,
or James Geary's excellent presentation here.

Thanks to my Draper Program colleague Seth Taylor Garrison for his help preparing this paper.

This blog is an abridged version of an essay given on Aug. 5, 2010 at the 5th International Conference on Interdisciplinary Social Sciences in Cambridge


Billow, R.M. (1977). Metaphor: A Review of the Psychological Literature. Psychological Bulletin, 84, 81-92.

Cutsforth, T.D. (1924). Synaesthesia in the Process of Reasoning. American Journal of Psychology, 35, 88.

Cytowic, R.E. (1989). Synesthesia and Mapping of Subjective Sensory Dimensions. Neurology, 39(6), 849-850.

Marks, L.E. (1974). On Associations of Light and Sound: the Mediation of Brightness, Pitch, and Loudness. American Journal of Psychology, 87, 173-188.

Marks, L. E. (1989). On Cross-Modal Similarity: The Perceptual Structure of Pitch, Loudness, and Brightness. Journal of Experimental Psychology: Human Perception and Performance, 15, 586-602.

Kohler, W. (1929). Gestalt Psychology (Original work published in 1938 ed.). New York: Liveright.

Click here for a complete bibliography of synesthetic research.

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