subliminal stimuli

Meaning: Subliminal stimuli are presented below the absolute threshold, the minimum intensity detected 50% of the time, so the person is not consciously aware of them. The sensory system can still process them, and they can influence later responses through priming, an implicit effect on memory and perception. Stimuli above the threshold are supraliminal.

On the MCAT: A passage describes a word or image flashed very briefly or masked, followed by a measured response, such as faster recognition of a related word. You label this subliminal priming and take it as evidence of unconscious (implicit) processing. Questions may link it to signal detection theory: the threshold shifts with expectation, motivation and fatigue, so what counts as subliminal varies across people and situations. Laboratory effects are generally small and short-lived, and evidence that subliminal advertising changes real purchasing is weak.

Common confusion: Subliminal does not mean the stimulus was never sensed, and it does not mean the stimulus controls behavior. Receptors can respond and the brain can process the information without awareness. Also keep it apart from the difference threshold (just-noticeable difference), which concerns the smallest detectable change between two stimuli that are both perceived. The MCAT sense is about sensory thresholds and implicit processing, not the Freudian unconscious.