Multisensory Integration in Complete Unawareness: Evidence From Audiovisual Congruency Priming

Abstract

Multisensory integration is thought to require conscious perception. Although previous studies have shown that an invisible stimulus could be integrated with an audible one, none have demonstrated integration of two subliminal stimuli of different modalities. Here, pairs of identical or different audiovisual target letters (the sound /b/ with the written letter “b” or “m,” respectively) were preceded by pairs of masked identical or different audiovisual prime digits (the sound /6/ with the written digit “6” or “8,” respectively). In three experiments, awareness of the audiovisual digit primes was manipulated, such that participants were either unaware of the visual digit, the auditory digit, or both. Priming of the semantic relations between the auditory and visual digits was found in all experiments. Moreover, a further experiment showed that unconscious multisensory integration was not obtained when participants did not undergo prior conscious training of the task. This suggests that following conscious learning, unconscious processing suffices for multisensory integration.

Cognitive Neuroscience: Integration of Sight and Sound outside of Awareness?

“…The results from the Faivre et al [3] study do not allow us unequivocally to answer this question. They do, however, provide important clues suggesting that the process may be taking place at the semantic level.…”

“…Earlier work has indicated that audible sounds can impact invisible pictures suppressed from awareness during binocular rivalry [2], but can auditory and visual signals interact when both are presented outside of awareness? A recent study by Faivre et al [3] provides an answer to this question by unequivocally demonstrating the interaction of subthreshold auditory and visual cues. Left unanswered, however, is whether this interaction represents genuine multisensory integration or, instead, arises from interactions at amodal, semantic levels of analysis (Figure 1).…”

“…In the new study [3], participants were briefly presented a priming stimulus made up of a pair of digits — one presented as a visual stimulus and the other as an auditory stimulus — that were sometimes identical (for example, a spoken ‘2’ and a printed ‘2’) and other times were not (for example, a spoken ‘8’ and a printed ‘2’). This prime was then followed by an audio-visual pair of target letters that were either identical or not.…”

What is consciousness, and could machines have it?

“…1). Subliminal priming generalizes across visualauditory modalities (7,8), revealing that crossmodal computations that remain challenging for AI software (such as extraction of semantic vectors or speech-to-text) also involve unconscious mechanisms. Even the semantic meaning of sensory input can be processed without awareness by the human brain.…”

Numerical Priming Between Touch and Vision Depends on Tactile Discrimination

“…First, unconscious processing of numerosity in vision is well documented, as invisible prime stimuli conveying either symbolic or nonsymbolic numerosity signals are known to induce priming effects under various techniques such as masking (Dehaene, Naccache, Le Clec', Koechlin, & Mueller, 1998), continuous flash suppression (Bahrami et al, 2010), or crowding (Huckauf, Knops, Nuerk, & Willmes, 2008;see Dubois & Faivre, 2014 for a comparison of various techniques used to make stimuli invisible). Second, cross-modal unconscious effects pertaining to numerosity processing are now well established, notably between a subliminal (i.e., consciously unaccessible) visual prime digit and a supraliminal (i.e., consciously accessible) auditory target (Kouider & Dehaene, 2009), and even between two subliminal audiovisual stimuli conveying numerosity information (Faivre, Mudrik, Schwartz, & Koch, 2014). Yet, while low-level interactions between a supraliminal tactile stimulus and a subliminal visual one are documented (Lunghi, Binda, & Morrone, 2010), no study to our knowledge has investigated cross-modal influences from subliminal stimulus in the tactile domain.…”