Interval and ratio reinforcement contingencies as determinants of methadone's effects

Travis Thompson, Joseph Honor, Steven Verchota, James Cleary

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The effects of methadone hydrochloride on lever pressing rats maintained under multiple fixed-interval and fixed-ratio, or multiple variable-interval and variable-ratio reinforcement schedules equated for reinforcement density were examined. Under a multiple fixed-interval, fixed-ratio schedule overall response rate was decreased during both components but was most affected under the ratio schedule. Response rate decreases were due primarily to changes in running rate rather than pause time. Under a multiple variable-interval, variable-ratio schedule, overall response rate was also decreased by methadone, with the greatest decrease again occurring during the ratio schedule. These schedule-specific methadone effects are not due to differences in reinforcement frequency. Evidence for rate-dependency with methadone is not consistent across subjects.

Original languageEnglish (US)
Pages (from-to)743-747
Number of pages5
JournalPharmacology Biochemistry and Behavior
Issue number5
StatePublished - 1984


  • Methadone
  • Multiple fixed-interval fixed-ratio


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