What does Weber's law state about the relationship between stimulus intensity and perceived difference?

Weber's law pertains to the relationship between the intensity of a stimulus and the smallest detectable difference in that stimulus (also known as the just noticeable difference, or JND). According to Weber's law, the ratio of the increment threshold (the smallest change in stimulus intensity that can be detected) to the background intensity of the stimulus is a constant. This means that as the intensity of the stimulus increases, the difference that must be perceived also increases, but it does so in a proportional manner rather than in a fixed amount.

The correct answer reflects the notion that the perceived difference is maintained in a proportional (or linear) relationship to the stimulus intensity. For example, if the background intensity doubles, the perceived difference that is necessary for detection will also increase proportionally. This establishes a direct, linear relationship between stimulus intensity and perceived difference as long as the conditions specified by Weber's law are met.

This understanding is foundational in the field of psychophysics and provides insights into sensory perception, highlighting how humans perceive variations in stimuli rather than the absolute changes in intensity.