Development of Crossmodal Sound–Shape Correspondence: The Role of Intuitive Audio-Visual Physical Knowledge in the Bouba–Kiki Effect

Successfully navigating the world involves integrating sensory inputs and selecting appropriate motor actions. Yet, what information is perceived as belonging together? In addition to spatial and temporal factors, correspondences between sensory features are important. The Bouba-Kiki (BK) effect is a well-documented example of a sound-shape crossmodal correspondence, where people tend to associate pseudowords, such as “baba” and “kiki”, with round and spiky abstract shapes, respectively. Previous research suggests that the strength of BK associations varies with development: associations are weak early in development, up to 3 years of age, and strengthen with age. These findings suggest that sound symbolic associations could be experience-dependent and, to some extent, learned through statistical co-occurrence in the environment. Here, we investigate one mechanism that could explain changes in the strength of BK associations as children develop, namely changes in the strength of intuitive audiovisual knowledge of physical events (IP), an understanding of what sounds will be produced as objects move in the world. This study aims to investigate the relationship between intuitive audiovisual physical knowledge (IP) and Bouba-Kiki (BK) associations, Specifically, we examine whether individuals with stronger intuitive physics abilities also demonstrate stronger Bouba-Kiki associations and how this relationship develops across different age groups and also how participants’ performance in the BK and the IP task changes over the course of the experiment. Importantly, differences in intuitive audio-visual physical knowledge (IP) could underlie the individual differences and variability found in the strength of sound-shape crossmodal correspondences (BK) associations early in development. A total of 180 healthy English-speaking participants will be studied, with 60 participants in each of three age groups: 6–8, 9–11, and 18–35 years old. Participants will be recruited via email advertisements, as well as through the Connecticut Science Center (Hartford, CT) and the Acton Discovery Museum (Acton, MA). The study will be conducted online via Zoom or in person at our laboratory on campus or at various local science and children’s museums. Within a given age group, participants will be randomly assigned such that half will complete the BK task first and half will complete the IP task first. The basic task is a two-alternative forced-choice task: two images are displayed on a screen, one on the left and one on the right, and then a sound is played via headphones. Participants must judge which shape best matches the sound by pressing one of two keys on a buttonbox. In the BK task, the images are abstract round and spiky shapes, and the sounds are pseudowords (see Chow & Ciaramitaro, 2019). In the IP task, the images are pictures of real-world round or spiked balls, and the corresponding real-world sound produced when they roll (see Fort & Schwartz, 2022). Each participant will complete 16 trials of each task.