AP Psychology Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

Weber's Law is a principle in psychophysics that describes the relationship between the magnitude of a stimulus and the smallest detectable difference in that stimulus, known as the just noticeable difference (JND). According to this law, the JND is not a fixed amount but rather a constant proportion of the original stimulus. This means that the greater the initial intensity of the stimulus, the larger the total change needed for a person to perceive a difference.

For example, if you’re holding a very light weight, a small additional weight may be perceptible, but if you’re holding a very heavy weight, a much larger increase is necessary for you to notice a change. This law is commonly expressed mathematically, with the formula ΔI/I = k, where ΔI is the change in stimulus intensity, I is the initial stimulus intensity, and k is a constant that varies by sensory modality.

The other concepts provided do not pertain specifically to Weber's Law. For instance, the adaptation of senses over time relates to sensory adaptation, not the measurable difference in stimuli. The conversion of energy forms pertains to other areas, like sensory transduction, and the measurement of sound intensity is more aligned with concepts like sound pressure levels rather than the proportional differences addressed