Which statement best describes Weber's Law?

• A. The minimum detectable change is the same absolute amount regardless of intensity.
• B. The perceived magnitude increases linearly with stimulus strength.
• C. The threshold for detection is fixed across intensities.
• D. The just noticeable difference is proportional to the baseline stimulus intensity.

Answer: (D)

Weber's Law says that the smallest change in a stimulus that we can detect—the just noticeable difference—scales with how strong the original stimulus is. In practical terms, the required change is a constant proportion of the baseline, so ΔI / I remains the same across intensities. That means a soft sound needs only a small change to notice, while a loud sound needs a larger change, even though the proportional amount is the same. The statement describing the just noticeable difference being proportional to the baseline intensity captures this idea. The other options misstate the idea: the smallest detectable change isn’t fixed in absolute terms across intensities, perception isn’t simply linear with stimulus strength, and the detection threshold isn’t fixed across all intensities.