Unconscious processing of an abstract concept.

At any single moment, people are bombarded with arrays of information, some entering conscious awareness (supraliminal), fueling a rich phenomenal experience of the environment, and some hidden from awareness (subliminal), unavailable for report. This observation raises fundamental questions regarding the function of consciousness. Accumulating evidence shows that processing of certain visual features and objects does not In the experiments reported here, we found novel evidence of unconscious processing of the abstract concept of the same-different relation. Consider two distinct items, A and B, and the pairs formed from them, AA, BB, AB, and BA. The items in the first two pairs belong to the category of sameness and the items in the last two pairs to differentness. This same-different concept holds at an abstract level; that is, the concept is derived from specific instances (such as the four pairs just given) and can be applied to novel ones (CC, CD, etc.). The ability to reason about abstract same-ness and differentness has long been thought to be the " keel and backbone " of human thinking and reasoning (James, 1890, p. 459). Some researchers suggest that it may be a uniquely human ability (Penn, Holyoak, & Povinelli, 2008; but see Wasserman & Young, 2010). In line with this view, it has been suggested that consciousness is necessary for evaluating conceptual relationships, such as the sameness and differentness of objects (Method We tested this hypothesis in the current experiments, in which participants first performed a masked go/no-go task (van Gaal, Ridderinkhof, Scholte, & Lamme, 2010) and then an objective-awareness test. Eighteen participants (6 men, 12 women; mean age = 19.6 years) were recruited for Experiment 1. In the masked go/ no-go task, two target objects were presented simultaneously and then masked by two annuli (Fig. 1a). The target objects were either presented briefly (for 16.7 ms or 33.3 ms) and were thus strongly masked and imperceptible to the participants' conscious awareness (nonvisible trials), or they were presented for a longer time (200 ms) and were thus visible to the participants (visible trials). The visible objects were selected from among four novel shapes, and the nonvisible objects were either square or diamond shapes (Fig. 1a). On each trial, the shape of the two target objects could be the same or different. The task was to press a button as quickly as possible when the shapes were either (a) visible and the same or …