By Guest Contributor Katherine Bryant
Katherine Bryant is a PhD candidate in Neuroscience at Emory University, where her research interests include network models of cortical connectivity, multi-modal association cortex, and human evolution. Her dissertation focuses on identifying human-unique specializations of the temporal lobe by comparing the white matter connectivity of cortex in humans, chimpanzees, and macaques. She is also receiving training in interdisciplinary graduate studies as part of a certificate in Mind, Brain, and Culture.

* This post was originally featured on The Neuroethics Blog.

Who are synesthetes?

[Describing the experiences of subject MMo] Eights are yellow, for example, a square feels like mashed potatoes, and the name Steve is somehow like poached eggs. (Cytowic p. 26)

“…I [asked the vendor] what kind of ice cream she had.  ‘Fruit ice cream,’ she said.  But she answered in such a tone that a whole pile of coals, of black cinders, came bursting out of her mouth, and I couldn’t bring myself to buy any ice cream after she’d answered that way…” (Record of patient “S”, Luria p. 82)

Colored alphabet,via Wikipedia Commons

The unexpected sensory pairings described above are the experiences of a minority of people, perhaps 4% of the population (Simner et al., 2006), known as synesthetes. Synesthesia is a perceptual phenomenon in which unusual linkages occur between sensory modalities – sounds may evoke colors, tastes may evoke shapes, or numbers may evoke spatial patterns – in all, over 40 unique pairings have been documented.  Synesthesia creates problems – it defies normal categories of clinical pathology, and yet is clearly different from what we might call “normal” or neurotypical perception. But examining the phenomenon can help us gain a greater understanding of how synesthetes perceive the world, how others perceive them, and in what ways neuroscience can help us better understand unusual neurological phenotypes – what we might call neurodiversity.

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