Studies using Posner’s spatial cueing paradigm have demonstrated that participants can allocate their attention to specific target locations based on the predictiveness of preceding cues. Four experiments were conducted to investigate attentional orienting processes operating in a high probability condition as compared to a low probability condition using various types of centrally-presented cues. Spatially-informative cues resulted in cueing effects for both probability conditions, with significantly larger CEs in the high probability conditions than the low probability conditions. Participants in the high (...) probability conditions reported little or no awareness of cue–target probabilities after task completion. Our results provide support for an implicit learning account of the proportion valid effect under experimental conditions involving spatially-informative central cues and relatively short stimulus onset asynchronies. (shrink)