“…An inverse relationship between response rate and magnitude of drug reinforcement (dose per infusion) has been found using d-amphetamine (Pickens and Harris, 1968), methamphetamine (Pickens, Meisch, and McGuire, 1967), cocaine (Pickens and Thompson, 1968a;Woods and Schuster, 1968), and methylphenidate, pipradol, and phenmetrazine (Wilson, Hitomi, and Schuster, 1971). All of the studies utilized a continuous schedule of reinforcement (CRF) where an increase in rate is accompanied by an increase in drug intake.…”