无意识如何影响人类的认知？或者说，无意识知觉在什么水平对人类的认知产生作用。由于方法和标准的限制，对上述问题的争论依然存在。当前对无意识知觉的研究主要集中在阈下启动的加工机制上，即启动刺激如何有效引发被试对目标刺激的加工。研究者提出知觉加工，中枢加工，反应加工以及行为触发等理论来解释阈下启动的心理加工机制。

Because of restricted by methods and criterion, subliminal priming is still disputed. Now the focus of subliminal priming is its mechanisms. Subliminal response priming has been considered to operate on several stages, e.g. perceptual, central or motor stages might be affected. At the same times, subliminal priming effects are affected by the temporal predictability of a stimulus onset. To account for these contradictory results, Kiesel A. et al. proposed a two-process model, but we still can’t draw a conclusion.