The document discusses psychophysical measurement of sensory thresholds, including absolute threshold and difference threshold. It describes how Weber and Fechner studied how sensitivity limits change with stimulus intensity. Weber's law states that the just-noticeable difference is a constant fraction of the starting stimulus intensity. Fechner developed this further into Fechner's law, which allowed calculating sensation magnitude based on stimulus intensity. However, Weber's law and Fechner's assumptions have exceptions, as difference thresholds are not always constant and just-noticeable differences may not be psychologically equal.

1. Psychophysical Measurement of Thresholds: Differential Sensitivity CHAPTER 1, Psychophysics the Fundamentals