The bouba/kiki effect is robust across cultures and writing systems

Abstract

The bouba/kiki effect-the association of the nonce word bouba with a round shape and kiki with a spiky shape-is a type of correspondence between speech sounds and visual properties with potentially deep implications for the evolution of spoken language. However, there is debate over the robustness of the effect across cultures and the influence of orthography. We report an online experiment that tested the bouba/kiki effect across speakers of 25 languages representing nine language families and 10 writing systems. Overall, we found strong evidence for the effect across languages, with bouba eliciting more congruent responses than kiki. Participants who spoke languages with Roman scripts were only marginally more likely to show the effect, and analysis of the orthographic shape of the words in different scripts showed that the effect was no stronger for scripts that use rounder forms for bouba and spikier forms for kiki. These results confirm that the bouba/kiki phenomenon is rooted in crossmodal correspondence between aspects of the voice and visual shape, largely independent of orthography. They provide the strongest demonstration to date that the bouba/kiki effect is robust across cultures and writing systems. This article is part of the theme issue 'Voice modulation: from origin and mechanism to social impact (Part II)'.

Keywords: crossmodal association; iconicity; perception; sound symbolism; universals.

Figure 1.

Bouba and kiki shapes used in the experiment (the names were not displayed in the online survey). The shapes were adapted from Bremner et al. [37].

Figure 2.

Spectrograms (a,b) with fundamental frequency marked as a red contour and oscillograms (c,d) of the pseudowords bouba (a,c) and kiki (b,d).

Figure 3.

Posterior distributions of the coefficients from the main model; contrast coding for order predictor: kiki-first = −0.5, bouba-first = + 0.5; weighted effect coding for script predictor: other script = −2.12, Roman = +1; horizontal black lines show the 95% credible interval; thick boxes the 50% interval; points show the median. (Online version in colour.)

Figure 4.

Posterior medians (coloured squares) of the proportion of matching responses (bouba = round shape; kiki = spiky shape) for each language with the corresponding 95% credible intervals (coloured vertical segments) from the Bayesian logistic regression reported in the body of the text; white diamonds indicate the raw descriptive averages; languages are ordered by increasing posterior means; the grey dashed line shows the baseline level (=50%). (Online version in colour.)

Figure 5.

(a) Posterior samples for the L2 script effect (model that excludes participants who use a Roman alphabet in their L1); (b) posterior samples for the orthographic bias score (model on non-Roman script languages only, excluding Greek and Russian). (Online version in colour.)

Figure 6.

Analysis of first trials only shows that bouba trials were more accurate than kiki trials; black boxes indicate posterior medians; error bars indicate 95% credible intervals.