Pigeons responded on multiple variable-interval variable-interval schedules of reinforcement in an open and a closed economy. Equal duration components were increased in duration while the component rates of reinforcement were held constant, the component schedules were reversed, and component duration was decreased. In the open economy, daily sessions were limited to 1 hr, and subjects were maintained at 80% of their free-feeding weights through supplemental feeding when necessary in their home cages. In the closed economy, subjects were housed in their experimental chambers and no deprivation regimen was enforced. Relative response rate decreased as components were lengthened in the open economy, whereas in the closed economy relative rate increased as components were lengthened. Response proportions overmatched reinforcer proportions to a greater extent at long component durations in the closed economy, but there was no systematic effect of component duration on responding in the open economy.Key words: multiple schedules, component duration, closed economy, variable-interval schedules, overmatching, key peck, pigeonsIn multiple schedules, two or more independent schedules of reinforcement, each correlated with a different stimulus, are alternated at some specified interval. The alternation of schedules, or components, typically occurs independent of behavior. The distribution of responses between the successive components of a multiple variable-interval schedule is well described by a power function that relates the number of responses emitted per component and the number of reinforcers obtained per component. This function, called the generalized matching law (Baum, 1974b), takes the form:in which P represents the rate of responding emitted within a component, R represents the obtained rate of reinforcement within a component, and the subscripts denote the components of a multiple schedule. The fitted parameter a represents a constant preference for one of the alternatives that cannot be accounted for by the obtained distribution of reinforcers (bias), and the fitted exponent b represents a metric by which changes in behavior produced by a given change in reinforcement can be measured, and is said to capture the degree to which matching takes place on multiple schedules. Perfect matching is the case in which b is equal to 1.0, whereas values of b less than or greater than 1.0 represent instances in which undermatching or overmatching has been obtained. The absence of bias is indicated by values of a equal to 1.0. McSweeney, Farmer, Dougan, and Whipple (1986)