IF ASKED which of the two figures below is a "bouba" and which is a "kiki," 98 percent of all respondents choose the blob as a bouba and the other as a kiki. The authors argue that the brain's ability to pick out an abstract feature in common--such as a jagged visual shape and a harsh-sounding name--could have paved the way for the development of metaphor and perhaps even a shared vocabulary. Image: VILAYANUR S. RAMACHANDRAN
Imagine a band of ancestral hominids about to invent language. Clearly, they did not begin by having a leader say, "Hey, look at this--let's call it a banana. All of you say after me, ba-na-na." Undoubtedly, though, the group had a set of capacities that prepared the ground for systematic verbal communication. Our studies of the neurobiological basis of synesthesia suggest that a facility for metaphor--for seeing deep links between superficially dissimilar and unrelated things--provided a key seed for the eventual emergence of language.
Humans have a built-in bias to associate certain sounds with particular visual shapes, which could well have been important in getting hominids started on a shared vocabulary. In addition, specific brain areas that process visual shapes of objects, letters and numbers, and word sounds can activate each other even in nonsynesthetes, causing people to expect, say, jagged shapes to have harsh-sounding names.