Size-invariant but location-specific object-viewpoint adaptation in the absence of awareness

Perceiving object viewpoint is important for appropriate action. Here we investigated whether viewpoint information could be represented in the absence of awareness, by measuring viewpoint adaptation aftereffect from visual objects rendered invisible through interocular suppression. Participants adapted to either a visible or an invisible line-drawing cube with unambiguous viewpoint, then viewed an ambiguous Necker cube and reported its perceived viewpoint. In both the visible and invisible adaptation conditions, participants more likely perceived the Necker cube in opposite viewpoint compared to the adapting cube. Interestingly, this viewpoint aftereffect was still observed when the adapting and testing cubes were different in size. However, when the testing Necker cube was in a different location, the viewpoint aftereffect was only observed following visible adapting cube, abolished when the adapting cube was invisible. Thus object viewpoint representation could be established without awareness, and such unconscious viewpoint representation is size-invariant but location-specific. Object viewpoint representation requires conscious awareness to be globally accessible.