“…It is with this goal in mind that we revisit the definition of the S Dp . The discriminative stimulus for punishment had been discussed long before O’Donnell (2001) proposed the term and symbol, S Dp (e.g., Chance, 1999; Malott et al, 2000; Michael, 1980; Miller, 1997; Sulzer-Azaroff & Mayer, 1991); however, at the time, people were using different symbols and there was no consensus as to what to call a stimulus correlated with punishment contingencies. The S Dp filled an important need, as precise and consistent terminology facilitates scientific communication within a discipline.…”