Reinforcer concentration effects on a fixed-interval schedule

Frances J. Blomeley, C. F. Lowe, J. H. Wearden

    Research output: Contribution to journalArticlepeer-review


    Four rats received training on a mixed FI 30-s FI 150-s schedule, where the different FI values were associated with different levers. During baseline, the reinforcer was a 30% concentration of condensed milk. During subsequent testing sessions, the reinforcer concentration was varied within sessions over values of 10, 30, 50, and 70%. Measures of behaviour were taken from the FI 30-s lever during trials where the reinforcer was delivered for responses on the other lever. Increasing the reinforcer concentration which began the interval (a) increased the time to start responding in the interval, and (b) increased the location of the response peak on the FI 30-s lever (often to values well above 30 s). Response rate at the peak, and spread of the response rate versus time function, changed much less with reinforcer concentration. The data are discussed relative to predictions derived from Scalar Expectancy Theory, the Behavioural Theory of Timing, and the Tuned-trace model. © 2004 Elsevier B.V. All rights reserved.
    Original languageEnglish
    Pages (from-to)55-66
    Number of pages11
    JournalBehavioural Processes
    Issue number1
    Publication statusPublished - 30 Jul 2004


    • Behavioural theory of timing
    • Fixed-interval (FI) schedule
    • Mixed FI
    • Reinforcer concentration
    • Scalar expectancy theory
    • Tuned-trace theory


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