herkkyyskynnys

Herkkyyskynnys, or the sensitivity threshold, is a concept in psychology and physiology that denotes the minimum intensity of a stimulus required for detection or conscious perception. It is modality-specific and varies between individuals and contexts. In psychophysics, the idea is linked to the idea of the smallest detectable stimulus and to how perception changes with stimulus intensity. The concept includes the absolute threshold—the smallest detectable stimulus in a given modality—and the differential threshold, or just noticeable difference (JND), the smallest detectable change in a stimulus. The study of these thresholds has roots in early psychophysics and has evolved with theories such as signal detection theory, which separates perceptual sensitivity from response bias.

Measurements are performed by presenting stimuli and recording whether they are perceived, using methods such as the method of limits, staircase, or adaptive procedures. Examples include the auditory threshold (minimum sound level detectable, often expressed in decibels SPL), the visual threshold (minimal luminance or contrast needed for detection), and thresholds in olfaction or touch. Thresholds are also considered across other senses, including taste and temperature.

Several factors influence herkkyyskynnys, including physiological state (age, health), attention and arousal, adaptation to ongoing stimuli, motivation, and prior experience. Environmental context and measurement conditions can also alter results. Variability between individuals means thresholds are often reported as averages with confidence ranges.

Applications include clinical assessment of sensory function, design of auditory or visual displays, ergonomics and safety standards, and research into perception and artificial sensing systems. The concept helps explain why some stimuli are noticed in one situation but not in another, and why thresholds can shift with learning, disease, or training.