ABSTRACT
Another term for threshold, a term used in psychophysics for the level of stimulus intensity below which the organism ceases to respond (or, conversely, above which they do). In humans, this is equated to conscious awareness. The possibility that below this level the individual may be unconsciously aware of it or somehow responding to it has long been debated and researched (see subliminal perception). Usage of the concept in psychophysics itself has somewhat declined since the advent of signal detection theory which rejected the notion of clear-cut thresholds.
