Just Noticeable Difference
The minimum change in a stimulus required for detection, with implications for change.
Also known as: JND, Weber's Law, Minimum perceptible difference
Category: Concepts
Tags: psychology, perceptions, changes, awareness, measurement
Explanation
The just noticeable difference (JND) or Weber's Law describes the minimum change in a stimulus that can be detected. The key finding: the JND is proportional to the original stimulus - a small change to a small thing is noticeable, but the same absolute change to a large thing isn't. The principle applies to: pricing (small price changes on expensive items go unnoticed), workload (incremental additions on heavy loads aren't felt), and gradual changes (slow drift escapes attention). Implications include: small changes can accumulate unnoticed until suddenly significant, gradual improvement or decline may not be perceived, and attention is relative not absolute. Applications include: understanding how problems grow invisibly, recognizing gradual quality drift, and using incremental change strategically. The concept explains: boiled frog syndrome (gradual change unnoticed), lifestyle creep (spending increases invisibly), and scope creep (project growth by small steps). For knowledge workers, JND suggests: watching for gradual drifts, making progress visible, and recognizing that small changes may not feel significant until they are.
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