Bouba-Kiki Effect

"Bouba" and "Kiki"
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Which one is "Bouba" and which one is "Kiki"? 95% to 98% of participants called the shape on the left "kiki" and the one on the right "bouba". This picture is used as a test to demonstrate that people may not attach sounds to shapes arbitrarily.

The bouba-kiki effect is a non-arbitrary mapping between speech sounds and the visual shape of objects. It was first documented by Wolfgang Köhler in 1929 using nonsense words. The effect has been observed in American university students, Tamil speakers in India, young children, and infants, and has also been shown to occur with familiar names.

It is absent in individuals who are congenitally blind and reduced in individuals with autism. The effect has recently been investigated using fMRI.


The bouba/kiki effect was first observed by German-American psychologist Wolfgang Köhler in 1929.1 In psychological experiments first conducted on the island of Tenerife (where the primary language is Spanish), Köhler showed forms similar to those shown at the right and asked participants which shape was called "takete" and which was called "baluba" ("maluma" in the 1947 version). Although not explicitly stated, Köhler implies that there was a strong preference to pair the jagged shape with "takete" and the rounded shape with "baluba".

In 2001, Vilayanur S. Ramachandran and Edward Hubbard repeated Köhler's experiment using the words "kiki" and "bouba" and asked American college undergraduates and Tamil speakers in India "Which of these shapes is bouba and which is kiki?" In both groups, 95% to 98% selected the curvy shape as "bouba" and the jagged one as "kiki", suggesting that the human brain somehow attaches abstract meanings to the shapes and sounds in a consistent way.2

More highlights of research that has been done since then:

  • A study by Maurer et al. (2011) found that even children as young at 2,5 years old may show this effect.3
  • A study by Ozturk et. al (2013) found that even 4-month-old infants have the same sound–shape mapping biases as adults and toddlers.4
  • A study by Sidhu and Pexman (2015) showed that individuals will pair names such as "Molly" with round silhouettes, and names such as "Kate" with sharp silhouettes. Moreover, individuals will associate different personality traits with either group of names (e.g., easygoingness with "round names"; determination with "sharp names"). This may hint at a role of abstract concepts in the effect.5
  • Studies by Fryer, Freeman & Pring (2014) and Hamilton-Fletcher et. al (2018) indicate that the effect seems to be dependent on a long sensitive period, with high visual capacities in childhood being necessary for its typical development. In contrast to typically sighted individuals, congenitally blind individuals have been reported not to show a systematic bouba/kiki effect for touched shapes.67
  • A study by Oberman and Ramachandran has indicated that autistic individuals do not show as strong a preference. Individuals without autism agree with the standard result 88% of the time, while individuals with autism agree only 56% of the time.8


In 2019, researchers published the first study using fMRI to explore the bouba/kiki effect. They found that prefrontal activation is stronger to mismatching (bouba with spiky shape) than to matching (bouba with round shape) stimuli. Interestingly, they also found that sound-shape matching also influences activations in the auditory and visual cortices, suggesting an effect of matching at an early stage in sensory processing.9


Ramachandran and Hubbard suggest that the kiki/bouba effect has implications for the evolution of language, because it suggests that the naming of objects is not completely arbitrary. Research has also indicated that the effect may be a case of Ideasthesia.10

See also

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