There are many claims of psychological and behavioral effects from subliminal stimuli (i.e., stimuli that cannot be perceived, i.e., seen, smelled or heard). Although the effects themselves may not be controversial (e.g., congruency priming), the claim that they arise from processing of actually subliminal stimuli is.

In this experiment we investigated a simple congruency priming effect (Stroop priming) using stimuli that were, according to standard definitions, subliminal (i.e., participants reported not perceiving them and could not discriminate them better than chance). Yet, we found the priming effects to be in line with perceived congruency rather than objective congruency between primes and targets, that is, when participants reported perceiving a RED prime they were fast in responding to a RED target even though the prime actually was BLUE (which should lead to a slow response).

As we also excluded a reversed causation explanation of these effects, the results show that occasional weak percepts and mispercepts are intermixed with no percepts in conditions traditionally claimed to be subliminal. As previous claims of subliminal effects often are very small, this result raises doubts regarding their subliminal nature and suggests that they can simply be residual supraliminal effects.


Sand, A., & Nilsson, M.E. (in press). When Perception Trumps Reality. Psychological Science. doi:10.1177/0956797616684681

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