Just noticeable difference

The Just Noticeable Difference (JND) is the smallest change in a stimulus—like brightness, weight, or sound—that a person can detect. For example, it’s the smallest increase in weight that makes you notice one object is heavier than another. JND varies depending on the type of stimulus and the individual. It helps explain how our senses perceive changes in the environment and is important in areas like marketing, design, and sensory testing, where understanding the limits of perception can influence how products are made or adjusted.