Representative dose-response curves show generally inverted-U dose-response curves for methylphanidate (MPH) in monkeys B (A), M (B), and T (C) and for atomoxetine (ATM) in monkeys B (D), M (E), and T (F) while they performed the delayed response task. Note: Results represent number correct of a possible 30 trials. Monkey B also scored one trial correct with MPH 0.4 mg/kg, but this score was not included here, because it was uncharacteristic for her behavior; higher doses were not tested in monkey B, because she was switched to a different study.