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Abstract:
Information integration across the senses is fundamental for effective interactions with our environment. A controversial question is whether signals from different senses can interact in the absence of awareness. Models of global workspace would predict that unaware signals are confined to processing in low level sensory areas and thereby prevented from interacting with signals from
other senses in higher order association areas. Yet, accumulating evidence suggests that multisensory interactions can emerge – at least to some extent- already at the primary cortical level [1]. These low level interactions may thus potentially mediate interactions
between sensory signals in the absence of awareness.
Combining the spatial ventriloquist illusion and dynamic continuous flash suppression (dCSF) [2] we investigated whether visual signals that observers did not consciously perceive can influence spatial perception of sounds. Importantly, dCFS obliterated visual awareness only on a fraction of trials allowing us to compare spatial ventriloquism for physically identical flashes that were judged visible or invisible.
Our results show a stronger ventriloquist effect for visible than invisible flashes. Yet, a robust ventriloquist effect also emerged for flashes judged invisible. This ventriloquist effect for invisible flashes was even preserved in participants that were not better than chance when locating flashes they judged ‘invisible’.
Collectively, our findings demonstrate that physically identical visual signals influence the perceived location of concurrent sounds depending on their subjective visibility. Even visual signals that participants are not aware of can alter sound perception. These results suggest that audiovisual signals are integrated into spatial representations to some extent in the absence of perceptual
awareness.
