Estimates of reinforcing effectiveness obtained for methamphetamine, MDPV, and α-PVP, normalized to cocaine for each of 4 rhesus monkeys (identified as 1, 2, 3, or 4). Top Panel: Data represent the maximum number of infusions of methamphetamine, MDPV, and α-PVP earned, normalized to the maximum number of infusions earned for cocaine for each monkey. Bottom Panel: Data represent the final ratio completed for the dose that maintained the maximum number of infusions of methamphetamine, MDPV, and α-PVP earned, normalized to the final ratio completed for cocaine for each monkey.