Suprathreshold

Suprathreshold is a term used in perception, psychophysics, and neuroscience to describe a stimulus whose intensity exceeds the threshold for perception or recognition. The threshold is the minimum level at which a given observer can detect or identify a stimulus under specified conditions. A suprathreshold stimulus thus produces a perceptual experience or a measurable neural response, while subthreshold stimuli remain below the level required for detection.

In psychophysics, suprathreshold stimuli are employed to study how perception scales with increasing intensity, including detection probability, loudness, brightness, and contrast. Researchers often examine how judgments change above threshold, such as the just noticeable difference (JND) and other scaling functions, to understand sensory processing and the limits of perception.

In neuroscience and clinical contexts, suprathreshold stimulation can evoke action potentials and percepts. For example, electrical stimuli above the neural firing threshold or tactile stimuli strong enough to be felt are considered suprathreshold. Controlling whether stimulation is supra-threshold is important in experiments and therapies, as it influences efficacy, safety, and comfort.

Thresholds are not fixed; they vary with attention, fatigue, adaptation, duration, context, and individual differences. Therefore, whether a stimulus is suprathreshold depends on the observer and the testing conditions. The concept helps describe how sensory systems respond to varying intensities and underpins methods for sensory assessment, stimulus design, and interventions that rely on perceptible stimulation.