MIL - MAL study of audiovisual crossmodal correspondences in young domestic chicks: sound-symbolism and relationship between Bouba - Kiki effect, visual shape, and auditory pitch.

Human languages contain both arbitrary word–meaning pairings and non-arbitrary ones, where the link reflects perceptual similarities. A well-known example of non-arbitrary mapping is the Bouba-Kiki effect, first observed by German psychologist Köhler in 1929, which demonstrates that we systematically associate certain auditory stimuli with specific visual shapes. Crossmodal correspondences of this kind have also been observed in non-human animals, suggesting that they may rely on general perceptual mechanisms rather than uniquely human linguistic processes. The present study investigates whether domestic chicks (Gallus gallus domesticus) present an early-emerging correspondence between auditory pitch and visual size. Sixty three-day-old chicks were tested in a two-choice task in which they selected between a large and a small circle while hearing either a high- or low-pitched sound. The animals could choose to go behind one of the panels, allowing assessment of the association between auditory and visual cues. The results revealed a partial crossmodal correspondence: chicks reliably matched high-pitched sounds with the small circle, while low-pitched sounds did not significantly increase choices for the large circle. This directional pattern indicates that chicks exhibit an early sensitivity to pitch–size relationships, although the mapping is not fully symmetrical at this developmental stage. Overall, findings support the idea that some crossmodal associations may emerge independently of language or experience, reflecting broader perceptual tendencies shared across species. They also contribute to growing evidence that domestic chicks provide a valuable model for exploring the evolutionary origins of multisensory integration.