Awareness is needed for contextual effects in ambiguous object recognition

Despite its centrality to human experience, the functional role of conscious awareness is not yet known. One hypothesis suggests that consciousness is necessary for allowing high-level information to refine low-level processing in a “top-down” manner. To test this hypothesis, in this work we examined whether consciousness is needed for integrating contextual information with sensory information during visual object recognition, a case of top-down processing that is automatic and ubiquitous to our daily visual experience. In three experiments, 117 participants were asked to determine the identity of an ambiguous object presented to them. Crucially, a scene biasing the interpretation of the object towards one option over another (e.g., a picture of a tree when the object could equally be perceived as a fish or a leaf) was presented either before, after or alongside the ambiguous object. In all three experiments, the scene biased perception of the ambiguous object when it was consciously perceived, but not when it was processed unconsciously. The results therefore suggest that conscious awareness may be needed for top-down contextual processes.