The Weber-Fechner Law is a principle in psychology that explains how we perceive changes in stimuli. It states that the perceived change in a stimulus is proportional to the original intensity of that stimulus. For example, if you are holding a light weight and add a small amount, you may notice the difference. However, if you are holding a heavy weight, the same small addition may go unnoticed. This law combines the ideas of Ernst Weber and Gustav Fechner, who studied sensory perception. Weber focused on the just noticeable difference (JND), while Fechner expanded on this to relate it to overall sensory experience.