Philosophy, Psychology and Neuroscience

Crossmodal correspondences: Crossmodal grouping by similarity or a weak form of synaesthesia that is common to us all?

All of us exhibit a tendency to match (or associate) sensory features in one sensory modality, either physically present, or merely imagined, with sensory features, either physically present, or merely imagined, in another modality. Such crossmodal correspondences have now been demonstrated between all combinations of senses, and affect everything from speeded responses to people’s performance in unspeeded psychophysical tasks. While some correspondences are culture-specific, others are likely universal (e.g., the correspondence between auditory pitch and visual or haptic size). Crossmodal correspondences, unlike other forms of crossmodal binding, such as the multisensory integration of shape or semantic information (e.g., the binding or pairing of the sight of a dog with the sound of a dog’s barking), tend to be initially surprising (in this regard being similar with synaesthesia). Intriguingly, the latest research has demonstrated that some animals (e.g., chimps), as well as very young (i.e., pre-linguistic) infants, are sensitive to a number of crossmodal correspondences thus ruling out a linguistic explanation of at least certain correspondences. I will discuss a number of the other plausible explanations that have been put forward over the years in order to account for the existence of crossmodal correspondences. I will question whether, as many have argued, crossmodal correspondences should be thought of as a weak form of synaesthesia that is common to us all. Instead, I will suggest that crossmodal correspondences may be better conceptualized in terms of the Gestalt principal of grouping by similarity.