What does the term 'just noticeable difference' refer to in Weber's Law?

The term 'just noticeable difference' (JND) refers specifically to the minimum change in a stimulus that can be detected by an observer. This concept is rooted in Weber's Law, which states that the ability to perceive differences in varying stimuli is proportional to the magnitude of the initial stimulus. In simpler terms, JND highlights the smallest difference in intensity between two stimuli that a person can notice; for instance, if you have a light that is very dim, a slight increase in brightness may be noticeable. However, if the light is already very bright, a larger increase may be necessary for a difference to be perceived. The essence of JND illustrates how human perception adapts to the proportionality of changes rather than fixed quantities.

The other choices do not accurately capture the meaning of the term. The average perception of stimulus intensity pertains to overall experience rather than the threshold of change. The threshold at which a stimulus is first perceived refers to absolute thresholds, not differences. Lastly, the maximum intensity a stimulus can reach before being perceived is not a concept related to just noticeable difference, as it involves the limits of perception rather than incremental changes in stimuli.