Just Noticeable Difference
Definition
Formally, Just Noticeable Difference (JND) can be defined as the magnitude of change in a stimulus necessary for it to be perceived as different from another stimulus, or as the smallest detectable difference between two stimuli (Stern and Johnson 2010).
History
To talk about the history of JND we need to talk about the history of Signal Detection Theory (Wixted 2020), and for that, we need to talk about a certain German scientist — Gustave Fechner.
Fechner was most famous for purporting two laws: Weber’s law and Fechner’s law, which state as follows:
Weber’s law: As stimulus intensity is gradually increased, the difference is at first imperceptible, but as the stimulus intensity increases still further, the change finally becomes detectable. This change is what we now call “just noticeable difference”.
- Weber’s law holds that \(\Delta I / I = k\), where \(k\) is the constant.
Fechner’s law:
Absolute vs. Difference Threshold
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References
Citation
@online{long2025,
author = {Long, Sheng},
title = {Just {Noticeable} {Difference}},
date = {2025-10-14},
langid = {en}
}