erotuskynnys

Erotuskynnys, in psychophysics, refers to the difference threshold—the smallest detectable difference between two stimuli that a person can perceive as distinct. It is closely related to the concept of the just noticeable difference (JND). The erotuskynnys is measured across sensory modalities, including vision, hearing, touch, taste, and temperature, and it can vary with the baseline intensity of the stimuli.

In experimental settings, researchers estimate the erotuskynnys using methods such as the method of limits, the method of constant stimuli, and adaptive staircase procedures. These approaches yield a value for the minimum change in a stimulus required for discrimination with a given probability, often around 50 percent.

A key principle in the study of erotuskynnys is Weber's law, which states that the ratio of the just noticeable difference ΔI to the baseline intensity I is approximately constant across many senses. The specific constant, the Weber fraction, depends on the modality and context and tends to be smaller for more sensitive senses and larger for less sensitive ones.

In Finnish research and practice, erotuskynnys is used to describe perceptual discrimination thresholds in experiments, product testing, and human factors work. It informs the design of displays, alarms, controls, and audio devices by indicating how large a change must be for users to notice it.

See also: perceptual threshold, Weber's law, just noticeable difference.