Show Reference: "The function of consciousness in multisensory integration"

The function of consciousness in multisensory integration Cognition, Vol. 125, No. 3. (December 2012), pp. 353-364, doi:10.1016/j.cognition.2012.08.003 by Terry D. Palmer, Ashley K. Ramsey
    abstract = {The function of consciousness was explored in two contexts of audio–visual speech, cross-modal visual attention guidance and {McGurk} cross-modal integration. Experiments 1, 2, and 3 utilized a novel cueing paradigm in which two different flash suppressed lip-streams cooccured with speech sounds matching one of these streams. A visual target was then presented at either the audio-visually congruent or incongruent location. Target recognition differed for the congruent versus incongruent trials, and the nature of this difference depended on the probabilities of a target appearing at these respective locations. Thus, even though the lip-streams were never consciously perceived, they were nevertheless meaningfully integrated with the consciously perceived sounds, and participants learned to guide their attention according to statistical regularities between targets and these unconsciously perceived cross-modal cues. In Experiment 4, {McGurk} stimuli were presented in which the lip-streams were either flash suppressed (4a) or unsuppressed (4b), and the {McGurk} effect was found to vanish under conditions of flash suppression. Overall, these results suggest a simple yet fundamental principle regarding the function of consciousness in multisensory integration – cross-modal effects can occur in the absence of consciousness, but the influencing modality must be consciously perceived for its information to cross modalities. \^{a}º Speech sounds were presented concurrently with visually suppressed lip-streams. \^{a}º Auditory–visual congruence influenced visual perception (viz., attention allocation). \^{a}º This relationship failed to influence auditory perception (viz., {McGurk} integration). \^{a}º Consciousness was a prerequisite for information conveyance beyond a modality.},
    author = {Palmer, Terry D. and Ramsey, Ashley K.},
    doi = {10.1016/j.cognition.2012.08.003},
    issn = {00100277},
    journal = {Cognition},
    keywords = {biology, multi-modality},
    month = dec,
    number = {3},
    pages = {353--364},
    posted-at = {2012-12-19 15:02:34},
    priority = {2},
    publisher = {Elsevier},
    title = {The function of consciousness in multisensory integration},
    url = {},
    volume = {125},
    year = {2012}

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Percepts can be processed (in certain settings) and acted upon without being conscious of them. This raises the question what is the use of consciousness.

Some people hold that consciousness is not needed for anything, but a side effect of perceptual processing.

One theory of the function of consciousness is that it is needed to integrate information from different modalities and processing centers in the brain and coordinate their activity.

It makes sense that consciousness could be important for multi-sensory integration.

According to Palmer and Ramsey,

"Multisensory integration refers to the process by which information from different sensory modalities (e.g., vision, audition, touch) is combined to yield a rich, coherent representation of an object or event in the environment."

Humans can learn to use the statistics of their environment to guide their visual attention.

Humans do not need to be aware of the stimulus they perceive to use them to guide their visual attention.

Stimuli in one modality can guide attention in another.

Humans can learn to use stimuli in one modality to guide attention in another.

Palmer and Ramsey show that lack of awareness of a visual lip stream does not inhibit learning of its relevance for a visual localization task: the subliminal lip stream influences visual attention and affects the subjects' performance.

They also showed that similar subliminal lip streams did not affect the occurrence of the Mc Gurk effect.

Together, this suggests that awareness of a visual stimulus is not always needed to use it for guiding visual awareness, but sometimes it is needed for multisensory integration to occur (following Palmer and Ramsey's definition).