Consider two abstract shapes. One is an amorphous, rounded blob with soft, curving edges. The other is a sharp, angular figure with jagged points. If you had to name one “bouba” and the other “kiki,” you would likely make the same choice as the vast majority of people. This phenomenon, where we link specific sounds to particular shapes, reveals a deep wiring in the human brain, hinting that our senses of sight and hearing are not as separate as they seem.
The Original Experiment
The first formal investigation into this link between sound and shape dates back to the 1920s. German-American psychologist Wolfgang Köhler, a proponent of Gestalt psychology, conducted a series of insightful experiments. In his 1929 study, he presented participants with rounded and spiky shapes and asked them to assign one of two made-up words, “takete” and “maluma,” to each shape.
The results were consistent. Participants, Spanish speakers on the island of Tenerife, almost universally paired the spiky shape with “takete” and the rounded shape with “maluma.” Köhler’s work provided the first scientific evidence that the brain forms connections between sensory experiences, laying the foundation for research into this effect.
The Science of Sound Symbolism
This phenomenon is a result of sound symbolism, where the sounds of words carry inherent meaning, independent of their definition. When saying “kiki,” the mouth performs sharp, abrupt movements. The ‘k’ is a voiceless plosive (a sudden release of air) and the /i/ vowel requires a taut, angular mouth shape, mimicking the visual concept of sharpness.
Conversely, “bouba” involves a different set of oral postures. The ‘b’ sound is made by pushing air through rounded lips, while the ‘ou’ and ‘a’ vowels are produced with a relaxed jaw and rounded mouth. This mirrors the soft contours of the curvy shape. This mapping of sound to visual properties is known as cross-modal correspondence, and neuroimaging suggests the angular gyrus helps integrate these sensory streams.
Cross-Cultural and Linguistic Evidence
To confirm the effect was not a quirk of Western culture, researchers have replicated the experiment globally. Studies with Tamil speakers in India and American college students found that 95% to 98% of participants made the expected bouba/kiki choice. This consistency points to a fundamental aspect of human cognition rather than a learned association.
Evidence also comes from groups with little exposure to written language. The Himba people of northern Namibia, who are largely non-literate, show a strong preference for the expected matching. The effect has been observed in toddlers and infants as young as four months old, suggesting the predisposition exists before language is fully developed. The effect’s strength can vary and appears less pronounced in individuals with autism, hinting at its connection to specific neural processing pathways.
Real-World Implications
The principles of sound symbolism have tangible applications in commerce, where marketing professionals leverage the kiki/bouba effect to shape consumer perceptions. A brand name with sharp, crisp sounds might be chosen for products seen as precise or fast, such as technology or sports cars.
Names with soft, rounded sounds are used for products meant to evoke comfort or indulgence, like lotions, pillows, or food items. This link between sound and meaning allows companies to build a brand identity from the moment a customer hears its name, making it a powerful tool in shaping our choices.