What role does temporal synchrony play in mid-level audiovisual crossmodal correspondences?

Temporal synchrony is widely recognized as one of the key factors facilitating the emergence of crossmodal correspondences and affecting their crossmodal effects. However, several issues regarding the definition of temporal synchrony and the mechanisms underlying its crossmodal effects remain open, depending on the specific experimental/perceptual context/stimuli used, as well as the influence of crossmodal congruency and structural (including isomorphic) crossmodal correspondences. In this review, we take a closer look at the literature that has been published in this area over recent decades in order to critically evaluate what is currently known concerning the crossmodal effects that are mediated by temporal synchrony. We focus especially on mid-level audiovisual crossmodal correspondences, defined as those that involve multi-element, or dynamic, auditory and visual stimuli. We examine the different experimental methodologies used and their limitations as well as the theoretical frameworks that have been proposed to account for the viewer's impression of (and the meaning/affect that is associated with) such experimental audiovisual displays, including those that are based on the 'Congruency-Associationist Model', Gestalt perceptual grouping, as well as the phenomenon of multisensory emergence. Finally, we outline several directions for future research on temporal synchrony in the context of audiovisual crossmodal correspondences.