Integrating information from invisible signals: the case of implied motion
53.317, Tuesday, May 14, 8:30 am - 12:30 pm, Royal Ballroom 6-8
Nathan Faivre1, Christof Koch1, 2; 1Computation and Neural Systems, California Institute of Technology, Pasadena, CA, USA, 2Allen Institute for Brain Science, Seattle, WA, USA
One key aspect of visual awareness is that it consists in an integrated experience, in which different features of objects (e.g., color, shape) cannot be perceived independently from each other. Accordingly, it has been proposed that consciousness must somehow relate to the capacity of the brain to integrate incoming sensory signals into a unified percept. This implies a lower level of integration for stimuli that are perceived at a subliminal, nonconscious level. However, this hypothesis has been challenged recently by empirical results revealing that incongruence between invisible objects and their backgrounds can still be detected, which suggests that visual awareness may not be necessary to detect semantic incongruence in visual scenes. Here, we asked whether nonconscious integration applies to other visual properties, independent of incongruity detection. We tested whether motion direction can be extrapolated from static stimuli implying motion (e.g., a picture of a horse running towards the left), both in the presence and absence of perceptual awareness. Relying on adaptation to motion, we found that visible - but not invisible implied motion was processed such as biasing the perception of moving-dots. This suggests that only visible implicit motion can activate direction-selective circuits involved in the processing of real motion. Nevertheless, this negative result in the invisible condition does not imply the absence of nonconscious integration for implied motion, as we found in another experiment that invisible stimuli implying motion could still elicit repetition priming effects. We conclude that spatial integration applies to invisible signals implying motion, and that the involvement of real motion circuits after adaptation to implied motion results from post perceptual processes which only occur with perceptual awareness.