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 for both positive and negative masking (i.e. the "handle" and "dip," respectively) are described. Sometimes, but not always, negative masking disappears with an appropriate re-description of stimulus magnitude.