“…The rate-dependency principle originated from Dews' (1958) suggestion that control rates of operant responding could explain why amphetamine differentially alters behavior maintained by schedules of reinforcement. Specifically, amphetamine often increases rates of responding under schedules that usually produce low control response rates [differentialreinforcement-of-low-rate (DRL): Kelleher, Fry, Deegan, & Cook, 1961;Sidman, 1956;Zimmerman & Schuster, 1962; fixed-interval (Fl): Clark & Steele, 1966;de Oliveira & Graeff, 1972]. In contrast, amphetamine usually decreases rates of responding under schedules that produce high control response rates [fixedratio (FR): Heffner, Drawbaugh, & Zigmond, 1974;Owen, 1960;variable-interval (VI): Bradshaw, Ruddle, & Szabadi, 1981;Lucki, 1983].…”