Psychopharmacology (2012) 220:771–785 In summary, we extended the characterization of ST chain schedules of self-administration using either an RI or a PR requirement on the seeking link, and we showed that changes in reward magnitude, reward omission, or α-flupenthixol treatment affected responding, depending on the type of the reinforcer and the schedule used. Therefore, ST chain schedules provide a useful addition to existing self-administration paradigms. The explicit separation of the acts of seeking and taking rewards endows these schedules with naturalistic validity, because in the real world, seeking out rewards and actually consuming them require different sets of action. Acknowledgments This study was supported by ZonMw (the Netherlands Organisation for Health Research and Development) Grant 91207006 (awarded to L.J.M.J.V., P. Voorn and A.B. Smit), ZonMw (the Netherlands Organisation for Health Research and Development)/National Institute on Drug Abuse (NIDA) Collaborative Grant 31180007 (awarded to L.J.M.J.V. and R.C. Pierce), and Brain Foundation of the Netherlands (Hersenstichting) Grant 13 F05(2).26 (awarded to L.J.M.J.V.). We thank S. Pouw for technical assistance. Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. References Aberman JE, Salamone JD (1999) Nucleus accumbens dopamine depletions make rats more sensitive to high ratio requirements but do not impair primary food reinforcement. Neuroscience 92:545–552 Aberman JE, Ward SJ, Salamone JD (1998) Effects of dopamine antagonists and accumbens dopamine depletions on time- constrained progressive-ratio performance. 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