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. Author manuscript; available in PMC: 2015 May 12.
Published in final edited form as: Behav Processes. 2013 Aug 29;101:89–96. doi: 10.1016/j.beproc.2013.08.012

Fig. 5.

Fig. 5

Representative joint distributions of Inter-Reinforcement Interval durations (IRI) and their associated mean inter-response intervals, 〈iri〉, from one bird responding for several sessions each on 3 different Variable Interval (VI) schedules, plotted against linear axes. The discrete character of the IRI’s arises from the way the VI schedules were implemented: The interval to the setting up of the next reinforcer was drawn from a uniform discrete probability distribution on a set of 10 intervals with equal logarithmic separations. The first peck after this interval elapsed delivered the reinforcer.