Conscious access to the unisensory components of a cross-modal illusion.

It is often claimed that binding information across sensory modalities leads to coherent, unitary mental representations. The dramatic illusions experienced as a result of intersensory conflict, such as the McGurk effect, are often attributed to a propensity of the perceptual system to impose multisensory coherence onto events originating from a common source. In contrast with this ssumption of unity, we report an unexpected ability to resolve the timing between sound and sight regarding multisensory events that induce an illusory reversal of the elements specified in each modality. This finding reveals that the brain can gain access, simultaneously, to unisensory component information as well as to the result of the integrated multisensory percept, suggesting some degree of penetrability in the processes leading to cross-modality binding.