Differential processing of invisible congruent and incongruent scenes: a case for unconscious integration.

Integration is held to be a key feature of conscious awareness. Some even argue that the latter cannot occur without the former. We tested this claim by presenting masked scenes depicting a person performing an action with a congruent or an incongruent object (e.g., a man pouring coffee into a mug or into a roll of toilet paper). The masked scenes were then followed by briefly flashed targets that again included a congruent or an incongruent object, and subjects were asked to judge targets' congruency as fast as possible. Reaction times (RTs) for targets preceded by perceptually invisible scenes that included an incongruent object were longer than RTs for targets that were preceded by congruent images. This implicit measure suggests that subjects processed certain relations between the object and its background--or at least between the object and another object in the scene--despite being unaware of either. Subjective and objective measures confirmed the invisibility of the masked scenes, ruling out partial awareness. These results suggest that incongruency between scene elements can be unconsciously processed even at impoverished presentation conditions, with reduced contrast and exposure durations as short as 33 ms. They provide evidence for ongoing contextual influences of unseen stimuli on the processing of a subsequent target.