Temporal Tuning of Continuous Flash Suppression for 3D Objects Reflects Intrinsic Dynamics of Visual Awareness

Understanding how visual information gains access to conscious awareness is a central issue in cognitive neuroscience. Continuous Flash Suppression (CFS) provides a powerful method to investigate this transition by reliably suppressing visual stimuli from awareness. Previous work by Zhu, Drewes, and Melcher (2016) showed that mask frequency influences suppression strength of 2D stimuli, with a peak at 6 Hz. However, whether these findings generalize to more ecologically valid 3D stimuli, and whether CFS strength depends on the eye viewing the stimulus, remains unknown. In this study, we presented a real 3D black disc to one eye, and the dynamic colorful mask to the other one, alternating the eye-of-presentation across blocks. In each trial, the mask flickered at one of ten frequencies ranging from 0 Hz (static) to 32 Hz. Participants responded by pressing a bar as soon as any part of the stimulus became visible. Reaction times (RTs) showed a clear dependence on mask frequency, with maximal suppression occurring at about 6 Hz, as previously found with 2D stimuli, and without reliable differences between right- and left-eye presentations. However, unexpectedly, RTs exhibited a robust bimodal distribution, possibly suggesting specific cognitive processing of 3D stimuli that deserve further investigation. Together, these findings support the view that CFS engages fundamental temporal mechanisms of visual awareness that are shared by both 2D and 3D stimuli and operate at a relatively early, binocular stage of visual processing.