Cross-correlation between auditory and visual signals promotes multisensory integration.

Humans are equipped with multiple sensory channels that provide both redundant and complementary information about the objects and events in the world around them. A primary challenge for the brain is therefore to solve the 'correspondence problem', that is, to bind those signals that likely originate from the same environmental source, while keeping separate those unisensory inputs that likely belong to different objects/events. Whether multiple signals have a common origin or not must, however, be inferred from the signals themselves through a causal inference process. Recent studies have demonstrated that cross-correlation, that is, the similarity in temporal structure between unimodal signals, represents a powerful cue for solving the correspondence problem in humans. Here we provide further evidence for the role of the temporal correlation between auditory and visual signals in multisensory integration. Capitalizing on the well-known fact that sensitivity to crossmodal conflict is inversely related to the strength of coupling between the signals, we measured sensitivity to crossmodal spatial conflicts as a function of the cross-correlation between the temporal structures of the audiovisual signals. Observers' performance was systematically modulated by the cross-correlation, with lower sensitivity to crossmodal conflict being measured for correlated as compared to uncorrelated audiovisual signals. These results therefore provide support for the claim that cross-correlation promotes multisensory integration. A Bayesian framework is proposed to interpret the present results, whereby stimulus correlation is represented on the prior distribution of expected crossmodal co-occurrence.