Syntactic processing in the absence of awareness and semantics

The classical view that multistep rule-based operations require consciousness has recently been challenged by findings that both multiword semantic processing and multistep arithmetic equations can be processed unconsciously. It remains unclear, however, whether pure rule-based cognitive processes can occur unconsciously in the absence of semantics. Here, after presenting 2 words consciously, we suppressed the third with continuous flash suppression. First, we showed that the third word in the subject-verb-verb format (syntactically incongruent) broke suppression significantly faster than the third word in the subject-verb-object format (syntactically congruent). Crucially, the same effect was observed even with sentences composed of pseudowords (pseudo subject-verb-adjective vs. pseudo subject -verb-object) without any semantic information. This is the first study to show that syntactic congruency can be processed unconsciously in the complete absence of semantics. Our findings illustrate how abstract rule-based processing (e.g., syntactic categories) can occur in the absence of visual awareness, even when deprived of semantics.