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A re-examination of responding on ratio and regulated-probability interval schedules

Pérez, Omar D. and Aitken, Michael R. F. and Milton, Amy L. and Dickinson, Anthony (2018) A re-examination of responding on ratio and regulated-probability interval schedules. Learning and Motivation, 64 . pp. 1-8. ISSN 0023-9690. PMCID PMC6264404.

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The higher response rates observed on ratio than on matched interval reward schedules has been attributed to the differential reinforcement of longer inter-response times (IRTs) on the interval contingency. Some data, however, seem to contradict this hypothesis, showing that the difference is still observed when the role of IRT reinforcement is neutralized by using a regulated-probability interval schedule (RPI). Given the mixed evidence for these predictions, we re-examined this hypothesis by training three groups of rats to lever press under ratio, interval and RPI schedules across two phases while matching reward rates within triads. At the end of the first phase, the master ratio and RPI groups responded at similar rates. In the second phase, an interval group yoked to the same master ratio group of the first phase responded at a lower rate than the RPI group. Post-hoc analysis showed comparable reward rates for master and yoked schedules. The experienced response-outcome rate correlations were likewise similar and approached zero as training progressed. We discuss these results in terms of a contemporary dual-system model of instrumental conditioning.

Item Type:Article
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URLURL TypeDescription Paper CentralArticle
Pérez, Omar D.0000-0002-4168-5435
Aitken, Michael R. F.0000-0001-9763-8999
Additional Information:© 2018 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license ( Received 1 April 2018, Revised 24 July 2018, Accepted 26 July 2018, Available online 13 September 2018. This work was funded by a UK Medical Research Council Programme Grant (G1002231) to ALM. ODP was funded by a PhD scholarship from CONICYT. ALM is the Ferreras-Willetts Fellow in Neuroscience at Downing College, Cambridge. We would like to thank Dr. George Vousden for providing advice on the running of this study.
Funding AgencyGrant Number
Medical Research Council (UK)G1002231
Comisión Nacional de Investigación Científica y Tecnológica (CONICYT)UNSPECIFIED
University of CambridgeUNSPECIFIED
Subject Keywords:Reinforcement schedules; Dual-system theories; Ratio schedule; Interval schedule; Goal-directed behavior
PubMed Central ID:PMC6264404
Record Number:CaltechAUTHORS:20181031-080422989
Persistent URL:
Official Citation:Omar D. Pérez, Michael R.F. Aitken, Amy L. Milton, Anthony Dickinson, A re-examination of responding on ratio and regulated-probability interval schedules, Learning and Motivation, Volume 64, 2018, Pages 1-8, ISSN 0023-9690, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90531
Deposited By: Tony Diaz
Deposited On:31 Oct 2018 19:54
Last Modified:10 Dec 2018 19:42

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