“…Examples are schedule-indueed polydipsia (SIP) (Falk, 1961), wheel running (Levitsky & Collier, 1968), air licking (Mendelson & Chillag, 1968), and pica (Villarreal, 1967). These behaviors are aequired gradually over the course of several sessions (Hymowitz, Freed, & Lester, 1970), are excessive in ex te nt (Falk, 1961), and eontinue unabated as long as the animals are exposed to the proper experimental eonditions (e.g., Hymowitz, 1971).…”