The brain's abstract dictionary
When presented with a curvy, amoeba-like shape and a sharp, spiky one, people from around the world are asked to assign them two nonsense names: "bouba" and "kiki." Overwhelmingly—between 95% and 98% of the time in some studies—people label the rounded form "bouba" and the angular one "kiki". This phenomenon is sound symbolism, the non-arbitrary connection between sounds and shapes. The effect suggests that the human brain does not create completely random associations for words and objects. Instead, it follows a set of underlying rules that cross cultural and linguistic boundaries.
The original discovery was made by German-American psychologist Wolfgang Köhler in 1929. He used the words "takete" and "maluma" and found a strong preference for pairing the jagged shape with "takete" and the rounded one with "maluma". The experiment was popularized in 2001 by neuroscientist V. S. Ramachandran and his colleague Edward Hubbard, who coined the now-famous "bouba" and "kiki" terms. One hypothesis for the effect relates to the physical movements of the mouth. To say "bouba," the lips make a rounded shape. To pronounce "kiki," the tongue makes sharp, quick movements against the roof of the mouth and back of the teeth. The sound's auditory properties appear to mimic its visual meaning.
A test in the Kunene
To determine if this effect was universal or a product of shared culture or written language, researchers needed to test it in a population isolated from these influences. The remote Kunene Region of northern Namibia was a test site. The region is arid and mountainous, with a population density of about 0.8 persons per square kilometer. It hosts the Himba, a semi-nomadic people who, at the time of the study, had limited exposure to Western culture and did not use a written language. This isolation meant their responses could not be influenced by the shape of letters in the Roman alphabet (e.g., a round 'b' vs. a sharp 'k').
In a 2013 study published in the journal Cognition, researchers presented the classic bouba/kiki test to Himba villagers. The results confirmed the universal nature of the shape-sound effect; the Himba participants consistently matched the rounded shape with "bouba" and the spiky one with "kiki," just as Westerners and Tamil speakers had done. This finding shows that at least some cross-sensory mappings are a fundamental part of human cognition, independent of language or education. The Kunene Region thus is a location for the study of how the brain organizes sensory input.