Refining bouba-kiki: Phonetic detail and object dimensionality in sound-shape correspondences

Abstract

Speakers cross-linguistically associate non-words that have round vowels, such as /buba/, with round shapes, and non-words without round vowels, such as /kike/, with spiky shapes (e.g. Kohler 1947). While this link has been attributed to cognitive associations between rounded vowel sounds and images of rounded lips, stimuli have conflated vowel roundness with other phonetic features that may also contribute to the correspondence. In this study, 200 listeners matched abstract objects with nonsense words that systematically varied by vowel frontness, consonant place of articulation, and consonant voicing. Listeners are significantly more likely to select a spiky shape over a round shape when given words with voiceless consonants, alveolar consonants, and front vowels; combinations of these features strengthen the effect. These findings are corroborated in the realm of real-world objects. 102 participants were more likely to name a rounded member of a real-world object class when hearing a word containing non-front vowels than when hearing a word containing front vowels. Further, two- versus three-dimensional object roundness influences the strength of this association. This study provides an empirically and phonetically refined perspective on the paradigm, demonstrating the benefit of considering both detailed phonetic correlates and refined object properties in work on sound symbolism.