The paper examines the correlation between, on the one hand, linguistic synaesthesia (that is, pairing of words referring to different sensory modalities, such as “bright sound” and “warm colours”), and, on the other hand, neurophysiological interactions between different sensory stimuli (that is, a percept in a given sensory modality, for example vision, elicited by a stimulus belonging to a different sensory modality, for example audition or smell). The authors take as a starting point Williams’ hypothesis about the hierarchy of synaesthetic pairings, and discuss it concerning universality, directionality, sensory categories and usage of corpora. Then, the authors conduct an empiric corpus-based study of Italian synaesthetic pairings, whose results support the theoretical discussion. In total, their findings show a strong parallel between linguistic synaesthesia and neurophysiological interactions between different sensory stimuli. This suggests that linguistic synaesthesia is affected by tendencies similar to the rules underlying the perceptual association of distinct sensory modalities.