How stable are taste-shape crossmodal correspondences over time?

The present research investigates the stability of taste-shape crossmodal correspondences (i.e., how people non-randomly associate tastes and visual shapes, such as sweetness matched to roundness) over time, exploring the temporal dimension of crossmodal interactions. While previous research has established the existence of various taste-shape crossmodal correspondences, this study addresses their consistency over time through a test-retest paradigm. Drawing parallels with the concept of synesthesia, in which stability is used as a criterion, the research focuses on taste-shape associations, a domain not previously explored for temporal stability. Participants rated the perceived curvature and symmetry that they associated with taste words (sweet, umami, sour, salty, and bitter) and their liking of tastes and shapes. The same participants performed this task three times over a 2-week period. The results consistently replicated previous findings, revealing that sweet tastes were perceived as significantly more curved and symmetrical than other tastes, and umami was rated as more curved and symmetrical than sour, salty, and bitter tastes. Notably, the study found moderate-to-substantial test-retest reliability for the majority of the taste-shape correspondences, indicating robust stability over time. Analyses suggested that differences in assessments between test and retest sessions were primarily due to random error, with no systematic biases. However, a small subset of participants showed significant differences from other participants in their associations, particularly for umami-related correspondences. This research contributes to our understanding of taste-shape correspondences by demonstrating their temporal stability, offering insights into the dynamics of taste, curvature, symmetry, and liking. We posit that consistency might be used as a criterion supporting the existence of a given crossmodal correspondence. The findings have implications for product design and marketing, emphasising the importance of considering temporal aspects when capitalising on crossmodal correspondences in creating product expectations and experiences.