The automatic and non-automatic aspects of unconscious visual processing

Past studies have documented various unconscious influences on a conscious task. However, what characteristics enable an unconscious effect remains elusive. Specifically, in this study we examined the importance of automaticity of unconscious processing and asked (1) When different unconscious information co-exists, will automated information be prioritized? (2) Does unconscious processing share limited attentional resources with conscious processing? We adopted a Stroop paradigm and measured how color (lowly automated) and word (highly automated) consistency between a subliminal prime and a supraliminal target influenced participants’ responses on the target. While keeping all other procedure and manipulation identical, participants were either instructed to name the color (Stroop condition) or word (Reverse Stroop condition) via button presses, leading to differential attentional load in the two task conditions. In the word-naming task, we showed that word but not color inconsistency slowed down the response time to the target, suggesting that automatic semantic activation was prioritized. Critically, during color naming, the same effect occurred only after a significant practice effect on the color naming (i.e. reduction of response time) was obtained, suggesting that lowering attentional load of a conscious task released additional attentional resources to enable the unconscious semantic effect. These findings were later replicated in separate experiments that isolated the color and word aspects of the prime. Across all experiments, chance rate performance on a 2-alternative-force-choice task of the subliminal prime location indicated that the interocular suppression was successful. We argue that information automaticity may be one determining factor of an unconscious effect. However, unconscious processing shares attentional resources with conscious processing in the current paradigm, showing its non-automatic nature. These results present a new framework to reconsider the interaction between conscious and unconscious visual information.