The history of dipper functions.

Dipper-shaped curves often accurately depict the relationship between a baseline, or "pedestal," magnitude and a just noticeable difference in it. This tutorial traces the 45-year history of the dipper function in auditory and visual psychophysics, focusing on when they happen and why. Popular theories of both positive and negative masking (i.e., the "handle" and "dip," respectively) are described. Sometimes, but not always, negative masking disappears with an appropriate redescription of stimulus magnitude.