Matching sounds to shapes: Evidence of the bouba-kiki effect in naïve baby chicks

Humans across multiple languages spontaneously associate the nonwords "kiki" and "bouba" with spiky and round shapes, respectively, a phenomenon named the bouba-kiki effect. To explore the origin of this association, and whether it is unique to humans, we tested the bouba-kiki effect in baby domestic chickens (Gallus gallus). As a precocial species, chicks can be tested shortly after hatching, allowing us to control their pretest experiences. Similar to humans, both 3-day-old [Experiment 1 (Exp. 1)] and 1-day-old (Exp. 2) chicks spontaneously choose a spiky shape when hearing the "kiki" sound and a round shape when hearing the "bouba" sound. Results from naïve young animals suggest a predisposed mechanism for matching the dimensions of shape and sound, which may be widespread across species.