PREFERENCE FOR UNSEGMENTED INTERREINFORCEMENT INTERVALS IN CONCURRENT CHAINS

Abstract

Five pigeons were trained under concurrent‐chain schedules in which a pair of independent, concurrent variable‐interval 60‐s schedules were presented in the initial link and either both variable‐interval or both fixed‐interval schedules were presented in the terminal link. Except for the baseline, one of the terminal‐link schedules was always a two‐component chained schedule and the other was either a simple or a tandem schedule of equal mean interreinforcement interval. The values of the fixed‐interval schedules were either 15 s or 60 s; that of the variable‐interval schedules was always 60 s. A 1.5‐s changeover delay operated during the initial link in some conditions. The pigeons preferred a simple or a tandem schedule to a chain. For the fixed‐interval schedules, this preference was greater when the fixed interval was 60 s than when it was 15 s. For the variable‐interval schedules, the preferences were less pronounced and occurred only when the changeover delay was in effect. For a given type of schedule and interreinforcement interval, similar preferences were obtained whether the nonchained schedule was a tandem or simple schedule. The changeover delay generally inflated preference and lowered the changeover rate, especially when the terminal‐link schedules were either short (15 s) or aperiodic (variable‐interval). The results were consistent with the notion that segmenting the interreinforcement interval of a schedule into a chain lowers the preference for it.