Unconscious numerical priming despite interocular suppression

Whether high-level properties of stimuli rendered invisible by interocular competition can influence perception and behavior remains controversial. We studied whether suppressed and invisible symbolic and nonsymbolic numerical stimuli can elicit priming. First, we established that participants were objectively unable to discriminate numerical prime stimuli when interocular suppression rendered them invisible. Next, we asked participants to enumerate a visible target set of items after being exposed to a suppressed, invisible (nonsymbolic or symbolic) prime set. Both symbolic and nonsymbolic unconsciously perceived numerical primes induced robust priming effects that were specific to the numerical distance between the target and prime. Comparison with a no-prime condition revealed that primes larger than targets interfered with target enumeration and primes the same as or smaller than targets facilitated target enumeration. Taken together, our findings provide clear evidence for high-level processing of stimuli rendered invisible through interocular suppression.