Learning of predictive relations between events depends on attention, not on awareness

It is generally assumed that storing predictive relations between two events (E(1) consistently precedes E(2)) in memory as bi-directional associations does not require conscious awareness of this relation, whereas the formation of unidirectional associations that capture the direction of the relation (priming e(1) activates e(2), but e(2) not e(1)) does. This study reports a set of experiments demonstrating that unidirectional associations can be formed even when awareness of the relation is actively prevented, if attention is "tuned" to process predictive relations. When participants engaged in predicting targets based on cues in an unrelated task before the actual acquisition phase, unidirectional associations were formed during this acquisition phase even though E(1) was presented subliminally. This suggests that although processing the relation between events may often be accompanied by awareness of this relation, awareness is not a prerequisite for the formation of unidirectional associations.