High-level face shape adaptation depends on visual awareness Evidence from continuous flash suppression

When incompatible images are presented to the two eyes, one image dominates awareness while the other is rendered invisible by interocular suppression. It has remained unclear whether complex visual information can reach high-level processing stages in the ventral visual pathway during such interocular suppression. Here, we asked whether basic face shape, which is thought to be encoded in areas of the ventral stream, can be processed without visual awareness. We measured aftereffects induced by prolonged exposure to distorted faces during continuous flash suppression. Despite constant physical stimulation, in some trials the adaptor face was fully suppressed from awareness, while in other trials it overcame suppression and became partially visible. Aftereffects were induced even by entirely invisible adaptors, albeit reduced compared to partially visible adaptors, and only when adaptor and test stimuli were presented in the same size to the same eye. However, when adaptor and test stimuli were presented to different eyes or to the same eye but in different sizes, aftereffects were restricted to partially visible adaptors. These results suggest that a monocular, low-level component of face shape adaptation escapes interocular suppression and can proceed without visual awareness. By contrast, high-level components of basic face shape encoding involving ventral stream processing are eliminated by interocular suppression and require visual awareness.